Home | Aquarium Equipment | The Best Aquarium Filters for Goldfish

The Best Aquarium Filters for Goldfish


Uploaded to Wikipedia Commons by Heptagon

Although goldfish made their debut as pets over 2,000 years ago, their needs are not always understood by those new to fish-keeping.  Because the average pet store goldfish is small and inexpensive, they are sometimes viewed as “beginner’s pets” that need little care.  Add to this the fact that many people remember “Grandma’s goldfish that lived for years in a tiny bowl”, and it’s easy to see why most meet untimely ends (well-cared for goldfishes can live into their 20’s – and sometimes to twice that age!).  Folks who buy a single goldfish usually do not want to be bothered with a filter, but the lack of filtration is by far the main reason for failure with these otherwise hardy fishes.  However, there is a filter that needs no pad or carbon changes, and which becomes more effective with age – custom made for busy, “filter-shy” fish enthusiasts.  Today we’ll take a look at it and other simple options that will lessen your workload and improve your goldfish’s quality of life.


Goldfish Do Not Stay Small!

When considering a goldfish, it’s important to realize the potential size your pet will reach.  Goldfish are available in a wide variety of colors, 4 tail-shapes, 3 body-shapes and 3 eye-types, but are all of the same species, Carassius auratus auratus.  Those known as comets – the basic pet store or “non-fancy” goldfish – can easily reach 8-12 inches in length.  Sixteen-inch long individuals have been recorded; in fact, I have seen several feral goldfishes near that size in the Bronx River, mixed in with breeding aggregations of carp (I must check if hybridization is possible…).  Fantails, moors and other strains tend to be shorter in length than comets, but they get quite hefty.

Veil Tail

Uploaded to Wikipedia commons by Bechstein


True, improperly-kept goldfishes will become stunted, and may survive in that state for several years, but this is not to be encouraged – and certainly not a lesson to be teaching the children for whom single goldfishes are often purchased.  When fully-grown, your pet will need a 20 gallon aquarium in which to live; plan on a 30 gallon for a pair.


The Ultimate Goldfish Filter

Although now largely-ignored by hobbyists, (perhaps they are “too simple”!), undergravel filters were once considered indispensable by serious aquarists, and are still relied-upon by many public aquariums today.  In zoos and at home, I’ve used these highly-effective filters in aquariums housing creatures ranging from seahorses to alligator snapping turtles, always with great results.


t204151gWhen considering undergravel filters, it’s important to bear in mind that biological filtration – the breakdown (by aerobic bacteria) of ammonia to nitrites and nitrates – is the most important function of a filter (please see article below).  And it is at this aspect of filtration that undergravels excel.  Simply-put, an undergravel filter turns your aquarium’s substrate into a giant, living, biological filtration unit.  What’s more, the filter plate does not take up important living space and, being hidden below the gravel, allows for the creation of pleasing aquascapes.  Best of all, there are no cartridges or filter mediums to clean or replace! 


Water Changes

Regular partial water changes are essential to maintaining water quality and fish health…regardless of tank size, filtration method, or fish species.  When doing partial water changes, be sure to use a manual or battery-operated gravel washer.  In this way, you will remove debris trapped in the substrate along with the water…that’s all the maintenance your undergravel filter will need!


Black Moor

Uploaded to Wikipedia Commons by ﻯναოթ€ռ


Undergravel filters have another characteristic that suits them well for use with goldfish.  Goldfish evolved in slow-moving waters, and they cannot abide fast currents; fantails, lionheads and other round-bellied varieties are especially-weak swimmers.  Yet they produce a good deal of waste, and do best in aquariums equipped with powerful filters (which usually put out strong outflow currents).  Undergravel filters discharge clean water through two tubes that reach to the water’s surface…even when very powerful air pumps are used, outflow currents remain mild.  You can check out a wide variety of air pump styles and sizes here; please post below if you need assistance in choosing a pump.


Increasing Your Filter’s Efficiency

Power heads can be used in place of air pumps if you need to increase water flow through the gravel bed.  You can also set up a reverse-flow system, which will lessen the amount of detritus that becomes trapped in the substrate; please post below for details.


Commercially-available aerobic bacteria (i.e. Nutrafin Cycle) can be used to jump-start your filter or to boost the beneficial bacteria populations that have developed naturally.


Other Goldfish Filters

From simple corner filters to state-of-the art canisters, there is a huge array of other filtering options for goldfish owners.  Please share your thoughts and experiences by posting below.

Further Reading

Aquarium Filtration: Understanding the Nitrogen Cycle

Making the Most of Undergravel Filters


  1. avatar

    I bought several “feeder fish” for a turtle that I was nursing back to health. He ate 10, but 2 lived two weeks in the aquarium. Once I realized that I was buying food for the feeder fish, they got pulled out and moved to their own tank. That was 4 years ago, and have been joined by 2 more “feeder fish” that I “rescued”, and they all live in a 40 gallon tank – the turtle, a snapper, has since been relocated to a pond…. (FYI – a snapper laid 24 eggs in a pile of sand on my driveway; they couldn’t stay there, so as soon as she left, I relocated the eggs to a flower pot; 22 eggs hatched in one day, and were carried to the pond; 1 egg hatched a few days later, but “he” wasn’t “right” and I over wintered “him” indoors until he was big enough to go out the next spring; the last egg was a dud…)

    The 4 gold fish are large – 5-6″ each. I’ve got an air bubbler and a 40 gallon filter running; I do near full water changes every 4-6 weeks, but am constantly battling algae and water discoloration.

    Any suggestions? I believe the orange water has to do more with the dyes in the fish food – I don’t want to purchase food that “intensifies the gold color”, but there’s little out there that doesn’t. They LOVE romaine lettuce, but feeding them that guarantees a gucky tank in days….

  2. avatar

    Hi Nancy,

    Amazing how snappers find open soil, isn’t it?…I’ve had them show up on newly dumped heaps of sand 1/4 away from the river, at the Bx Zoo.

    What type of filter do you have…this may be a factor.

    4 large fish in a 40 is pushing the limits…it can be managed, but you’ll need to be vigilant.

    Algae is largely dependent upon the amount of light the tank receives, although nutrient levels (fish waste, etc) are important as well. Some species are very difficult to eliminate; algicides can be useful, but must be used with care.

    You may be better off doing smaller, partial weekly or bi-weekly changes, so that water quality does not deteriorate so far before each change.

    I’ve never seen any evidence of discoloration due to foods; stay with Tetra min or another long-established brand.

    Please let me know filter model/details, best, Frank

  3. avatar

    Hi, Frank. I have been running an Aqueon “quiet flow” filter for a 50 gal. tank. However, I just purchased a Fluval Aqua Clear filter for 40 – 70 gal. Any thoughts?

    As for the water – I do have a problem, particularly in the winter, with the sun hitting the tank directly during the day (it’s across the room from my doorwall) contributing to algae growth. But I’ve never figured out why my water goes ORANGE, sometimes just days after a near complete water purge. I’ve been using my tap water – it’s well water treated with a softener that removes the rust.

    The fish are healthy enough. 40 gal might be tight for 4 goldfish, but a larger tank will only result in larger goldfish…! My largest grew 2 inches within a few months of going from a 20 gal tank to this one…


  4. avatar

    Hi Nancy,

    Filter sounds fine…I’ve heard other unusual reports re well water – wondering there is some type of reaction involving the softener. I have no experience with this, just guessing, but I’ve not run across anything similar involving food.

    Yes..that’s the trouble with goldfish..unless they are in a pond, one winds up with the same fish/water ratio in time…tough customers! Best, Frank

  5. avatar

    And I would have loved to release them to the pond behind my house, but after last winter – so much snow and ice that we lost almost all the wildlife (snappers, bull frogs, musk rats) – I wouldn’t take the chance….

    Thanks for your input! I’ll try the new filter.

  6. avatar


    Odd that native species had severe losses…is it an artificial pond? Where are yiou located. Avoid releasing goldfish in any event…they take over, completely change ecology , especially in closed systems like ponds/lakes. Best, Frank

  7. avatar

    I’m in southeast Michigan. I sent a note to the Michigan DNR; they responded that with the cold and snow cover we had last year, the lakes and ponds became deprived of oxygen, and there was significant aquatic losses throughout the region. You can’t throw a stone in my region of the state without hitting a pond/river/lake, and no one I know heard a single bull frog all season. Sad.

    As for goldfish disrupting the ecosystem – the pond I was referring to is a glorified, 2 acre puddle that the Township determined was okay to be the storm drain dumping ground for the $million home subdivision behind my property. Not spring fed, no water system to contaminate anything downstream. Full of frogs and turtles, and nothing else…. Goldfish couldn’t hurt it!

  8. avatar

    Interesting re the winter losses, thanks. We have similar ponds etc here in NY and elsewhere. But even in very disturbed systems, the plankton and plants support the food web. Breeding populations of goldfish remove far more plant life than native species, along with larger planktonic species; they also stir up the bottom to a greater degree than natives…the system collapses..tadpoles lose their food base, and so on. If there are snappers and herons, however, goldfish rarely survive unless released in large numbers, as they are easy marks. Hope this winter s better, Frank

  9. avatar

    Just wondering, I have three rescued feeder goldfish and two orandas which I recently moved from a 35 gallon tank to a 55 gallon tank. I have a 75 gallon Topfin tank side carbon filter and an Aqueon 50-70 gallon filter, plus a large 6″ x 10″ sponge filter bubbler. I add a tbsp of aquarium salt with each 10% water change. Is this going to be enough to provide a clean and healthy environment for these large 3-6″ goldfish if I do regular 5-10% water changes weekly with gravel vacuuming? The tank stays at about 68-70F, and I am feeding once in the morning and once at night: Goldfish flakes, bloodworms a few times per week, and spirulina tablets. I’m also concerned about maintaining clear water since the tank is in my living room. Your thoughts? Thank you.

  10. avatar


    You should be fine with the filters..water changes will be very impt; stay with 10% weekly if that works, increase volume if need be. Watch food amounts…skip at least 1 day each week, and use only 1 feeding on 1-2 other days. Keep gravel layer thin, using just a covering. This will enable you to remove more debris when you vacuum and will discourage formation of pockets of anaerobic bacteria. I wouldn’t add salt each week w/o checking salinity (use a simple hydrometer) to make sure salinity is not rising to a dangerous level. A simple ammonia test kit and pH test kit will help you to keep an eye on water chemistry – clarity is important, but water that appears “clean” can still be unsafe for the fishes. Please let me know if you need more info, enjoy, Frank

  11. avatar

    I have to say that sponge filters were my favorite for a long time, but now external power filters have taken their place in my heart. 😉 Goldfish are so messy that they require a heavier filtration system than tropical fish, so I think it is to the advantage of the goldfish keeper to have something more substantial churning out more water. I’ve actually used a 55/75 size filter for a 30 gallon tank with no problems. When in doubt, bigger is better in my opinion (as long as your fish are not having trouble swimming because of it).

  12. avatar


    Thanks very much for your feedback…yes, very important to be aware of currents when using powerful filters. Those equipped with spray bars etc. are especially useful for goldfish.

    Best regards, Frank

  13. avatar
    Savannah Oldham

    I have owned my beloved black Moore gold fish for almost 2 years now! I have tested the water in his tank multiple times and have had pet smart test it a few times and all levels seem clear. The water is heated enough the be in the “safe zone” and his tank is not in direct sunlight. I leave his light on for about 3-4 hours at a time. However, his water remains green. I feel like I have tried everything! Any suggestions would be amazing! Thank you.

  14. avatar

    Hi Savannah,

    Suspended algae is common in brightly-lit aquariums, and is difficult to eliminate as long as light levels remain the same…excess nutrients are also a factor, but if your nitrate levels are good then this is not likely the issue. There are some product to remove it safely, but it may return. Frequent partial water changes and a slight lessening of light levels may be useful. please see this article and let me know if you need more info. Best, Frank

  15. avatar

    Hey, I want to purchase a goldfish because they are the only pets I am allowed to house in college. I have done the research and I’m not gonna get a measly little bowl and deprive the poor thing to early death. I want to get a 10 gallon tank to start off with, some all natural gravel, and some nice aquatic plants. What aquatic plants, filtration system, and food would you recommend for one goldfish to be happy and lead a long life?

  16. avatar

    Hi Cuddy,

    Thanks for commenting! If sized right, most power filters will take good care of a 10 gallon goldfish tank. Since goldfish tend to be a little messy, we would suggest a good sized filter that turns your water over about 10 times an hour. A good 100 gph filter would be the Whisper 20 Power Filter or the AquaClear 20 Power Filter. Both are going to give you good flow rate, which will help you out especially if you want several goldfish.

    Pure Aquatic Goldfish Flakes are a good start for feeding. Most any freshwater aquarium plant would also be fine. Just select something you like in appearance. Hope that helps, let us know if you have any questions. Thanks!

  17. avatar

    So my family recently expanded to include two goldfish. My sister bought them for her daughter and they now reside in her “play corner” in our living room. The filter that came with the tank is absolutely horrible, the water is cloudy (partly because my sister didn’t get the water purifying drops I knew she would need. Because she thought they’d be fine in plain tap water), now we’ve lost one of the fish, the water is cloudy, smells like rot, and our last remaining fish, isn’t swimming around as energetically as he used to, and is beginning to get black patches from his head to the tip of his tail. We haven’t even had him two months yet. Is there anything I can do to save the little guy?

    Just so you know, its a 10 gallon tank.

  18. avatar

    Hi Nicole, It sounds like there are too main issues contributing here. 1) Its a new tank that isn’t established yet and 2) The tank is very small for goldfish. Goldfish produce A LOT of waste and need to be over-filtered to control the water quality. A 10-gallon tank is really too small for more than one very small goldfish and even that would need to be upgraded eventually to at least 30 gallons for one fancy goldfish like a fantail. Since this tank is also new, it would need to go through a cycling process (which can take up to 4-6 weeks) and there is a period during that cycling which cloudy water is common and completely normal.

    I would definitely look at getting a new filter for the tank – look for one rated for at least 30 gallons if you plan on keeping the goldfish in the 10-gallon tank for now. Most filters have some kind of filter cartridges or the ability to add them; I would recommend getting carbon into the cartridge which will help control the smell and some of the discoloration. Since the water sounds like its already pretty bad, you can start right now by doing a large water change and adding fresh dechlorinated water (tap water is fine as long as it is dechlorinated, it doesn’t need to be “purified”, per say). If you or your sister need any additional help, feel free to call and speak with our Fish Room staff at 717-299-5691, option 7.

  19. avatar

    Hello! Great post, I have 2 goldfish that my daughter got from the carnival she loves them and do not want them to die because she will be heartbroken but I’m trying to do all I can. Do you know a great aquarium I could buy for them to keep water clean I love the fact of the gravel filter but confused which to buy so do I not get one with the reg filters just buy a reg aquarium and add the gravel or what will I all need? my daughter is 4 & me and my husband are always busy working but would love some help to hopefully get this right without taking up too much time thank you so much!!

  20. avatar

    Hi Cole, thanks for commenting. Goldfish are pretty simple when it comes to fish, so you should be able to set up a habitat for them pretty easily. For two goldfish, a 10 gallon aquarium would be perfect. If you have the aquarium, all you need to do is add gravel, plants/decorations, a filter, a hood with light and a few accessories.

    Undergravel filters do work, if they are maintained properly, but they are also a filter technology that is somewhat outdated. It would be easier and much effective to go with a hang on the tank power filter. They run more gallons per hour, which is great for goldfish since they create a lot of waste.

    You can start by adding gravel, plants and water to your aquarium. If you are using chlorinated city water, you would want to use a de-chlorinator to remove chlorine and other heavy metals typically found in that type of water. Go ahead and start the filter. Once the temperature of the water reaches room temperature or is the same temperature of the water the goldfish are already in, you can go ahead and transfer them to the aquarium.

    For the first week or so, try to feed them small amounts, until the nitrogen cycle is complete. Once that finishes, your aquarium should be mature enough to handle added feedings. Hope that helps, please let us know if you have any other questions. Thanks!

  21. avatar

    My goldfish are always in the corner of the tank right up next to the filter is this normal or do I have a problem with the water or filter?

  22. avatar

    Hello Allison, That is usually a sign of stress, most often due to water quality. Have you tested the water, at the very least pH, Ammonia, Nitrite, Nitrate and temperature? How big are the fish and how many do you have? What size is the tank? How often do you do water changes on the tank and how much do you change?

  23. avatar

    Can I use an under gravel filter made for a 10 gallon tank on a 20 gallon one.

  24. avatar

    Hello Isabel, You can, but it won’t fit or work as well as one for the correct tank size.

  25. avatar

    Hi I have three gold fish in a 46 gallon bow front tank and i cant seem to keep the tank or water clean,, when i open the lid it smells horrible, it seems like their waste just sits on top of the water and im at a loss of what to do, i have a uv stabilizer and a aqua clear 70 running but i can barely see in the tank ,, Please help ! 🙁

  26. avatar

    Hi Heather, I’d recommend giving us a call and speaking with someone in our Fish Room (717-299-5691, option 7) so they can discuss the issues with your tank in more detail. There are a lot of things that could be at work here and we’d need more information about your tank and issue to be able to help you determine the best course of action to clear up the tank. What kind of goldfish are they and how big are they? Have you tested the water quality, and what are the values, especially for pH, Ammonia, Nitrite, Nitrate and Phosphate? You say you can barely see in the tank…is there algae? Is the water cloudy? What color is the cloudiness if it is…green, milky, brown, yellow? How often do you do water changes on the tank, and how much do you change at a time? How long has the tank been set up and established? How much and how often do you feed the fish? Our other blog articles on “The Nitrogen Cycle and Conditioning Period in New Aquariums“, “Why is My Aquarium Water Cloudy?”, and “How To Care For Carnival Fish” may help you in the meantime.

  27. avatar

    Hey guys, I recently installed an API Filstar XP-L (350 U.S. GPH) Canister Filter for my 20GAL. aquarium which holds a pair of 2 year old Moor´s, my question is that if its to much water flow??? I just installed it last night and I allready see water quality improvement but don’t want to stress or jeopardize my Moor´s… Thanks.

  28. avatar

    Hello Marco, That is a pretty large filter for that size aquarium. I would keep a close eye on the fish to make sure they are not being affected by the water flow and can swim easily. You can use the flow control on the filter to regulate the flow or use sponges or different output options to change the flow if it is too strong for the fish. You can contact our Fish Supplies staff at 717-299-5691 if you need some assistance on modifying the filter.

  29. avatar

    Thank you… What I ended up doing and worked is using some river rocks to soften the current on the bottom of the tank where the output flow is strongest and changed up the layout inside the tank to offer the fish a place with minimum current or water flow… What I just don’t get is that the Moor’s still like to play with the current sometimes!!! Thanks again.

  30. avatar

    Hi Frank, Can you recommend a budget friendly undergravel filter for a 30-gallon tank? Thank you 🙂

  31. avatar

    Hello Doree, Not many undergravel filters are available in the hobby anymore in favor of other filter types. The only undergravel filters that we still offer are the Lee’s Economy Undergravel Filters; the 29-gallon size would be the closest available for most 30-gallon tank but wouldn’t cover the entire bottom of the tank.

  32. avatar

    This type of filtration is my first filtration system way back in the early 90’s. It is cheap and only powered by air, I think this system is airlfit

  33. avatar

    Hi Frank. I have a 40 gallon rectangular tank with one fancy and one koi-type goldfish in it. I have two side filters: an Aqueon 20-gallon Whisper and Fluval 30-gallon Aqua Clear. As well I have 2 air stones.

    I do about a 20% partial water change every weekend because, as you know, these two 6-7 inch fish are moving waste machines!

    There is also a piece of driftwood in the tank and two live plants. The substrate is gravel.

    All of my water parameters are perfect except for the ammonia, which remains high no matter what I do. The biological filter is well-established and I am careful to not change the filter media too much or all at once but I can’t seem to get a fix on this ammonia. These 2 hardy guys are so far fine but I’m worried the continuing ammonia problem will eventually take its toll.

    Would a gravel filter help or should I perhaps exchange one of the side filters for a bigger canister?

    Thanks for any advice you might have. Love your blog!

  34. avatar

    Hi Diane, Frank is no longer with our blog but I’d be happy to help you out. Two 6-7 inch fish – especially fish that produce as much waste as goldfish – are really too big for a 40-gallon tank and that is contributing to your problem. When you say “koi-type goldfish”, do you mean a koi or a common Comet Goldfish? Comets grow up to about 10-12 inches and koi can grow to a couple feet in length…both of which do better in an outdoor pond or at least a tank over 100 gallons or so for the goldfish and much larger for a koi. Fancy goldfish don’t get as larger – usually about 6-8 inches – but that fish alone should have at least 40 gallons. I would look into a much larger aquarium for those two.

    In the meantime, upgrading your filters would help. Those gallon size recommendations that manufacturers advertise on most filters are usually pretty conservative and geared more towards lightly-stocked aquariums. For a 40-gallon goldfish tank, I would go with a filter recommended for at least 80 gallons and up, somewhere around 400-500 gallons per hour flow rate. A canister would give you more flexibility in the types and amounts of media you can use. You didn’t mention what type of media you use or change. Any biological media shouldn’t be changed since that houses a lot of the bacteria that will help break down the ammonia but any chemical media should be changed about every 2-4 weeks. If you don’t already, I would use ammonia-removing filter media. Hagen makes an Ammonia Remover Insert for the Aqua Clear or you can use a media that contains Zeolite. Zeolite looks similar to carbon but is white. A few products to look for are API Ammo-Carb or Ammo-Chips or Marineland Diamond Blend Premium Carbon-Ammonia Neutralizing Blend. I like Poly Filters as well; this is a pad that you can cut to fit your filter as needed.

    Hope that helps!

  35. avatar

    Hi Eileen – I’m hoping you can give some good advise. I have five large goldfish, the largest being just shy of 11″, which were just moved from a 30 gallon tank to a 120 gallon tank. I added two koi to the mix and then realized I have a high ammonia problem. I purchased the 120 gallon tank used. It came with gravel, decorations, wet/dry filter, an eheim 2228 canister and of course three Jack Dempsey’s. The Dempsey’s are in a 55 gallon and are now very happy but my goldfish are having a tough time. The ammonia is through the roof. We noticed the problem six days ago, we’ve done 20-30 gallon water changes three times and as of yesterday we lost one goldfish and the ammonia is still just as high as it was when we noticed the problem. We did use the existing gravel, decorations, filter media, etc which the last owner used. The tank was up and running when we purchased it but it did sit in our garage unused for approximately two weeks while we repaired the stand. We are at a loss, do we just continue to do 20-30 gallon water changes every other day?

  36. avatar

    Hello Andrea, I’m afraid that it sounds like there are a number of issues going on here. The 30 gallon they were moved from as well as the 120 gallon they are now in are overcrowded for fish that large, as is the 55-gallon with the Jack Dempseys. You will see water quality issues like high Ammonia in an overcrowded tank, especially with fish that produce as much waste and ammonia as goldfish and koi. These fish and at that size are more suited to a pond. Also, any new tanks need to go through a Nitrogen Cycle cycling process which will cause spikes in ammonia and nitrite naturally as the bacteria population in the tank becomes established enough to handle the waste. Ammonia-removing products like those mentioned in my previous reply above your comment may help. Also, a bacteria supplement may help get your aquarium established faster to help cope with the water quality issues; Microbe-Life Nite-out II are SeaChem Stability are good ones. You can give us a call at 717-299-5691 and speak with our Fish Room associates if you need more assistance.

  37. avatar

    We just got a new tank- been set up 3 days and is milky cloudy- I pulled the fish out and put them in a bucket until we can see the tank clear. NO ONE ever mentioned this cycle as something that would occur, and we thought the filter was not doing it’s job- changed the cartridge, thinking that that would help clear things, but apparently we’re wrong on that issue. Also pulled the plastic plants and moon rock out and cleaned them(w/H20). We do not have someplace, other than the bucket, to keep them in during this cycle. We do not want to endanger them(goldfish). There are no live plants in the aquarium. Should we put the plastic plants & moon rock back in now, or wait?
    Also, no one told us about which filter systems are best (and easiest to deal with)-we are not fish people. This started because the pet store owner passed out goldfish at Halloween last yr. Everyone else’s fish died- not ours…so we got a bigger tank and a couple companions- this darn 50 cent fish now has cost well over $100 (not impressed), and now we’re thinking we best get a gravel floor filtration system, but have no idea which is the best and easiest (the less time I, personally, have to deal with them, the better-I’m a fur animal person, not a fish lover-except for eating them!)
    Please tell us which is the best filter(floor gravel type). Also you mentioned a reverse-type system…how do we do that? Our tank is 10 gal. and came with a filter. We purchased a round sponge type of air pump. There are plastic plants, a moon rock, and glass or plastic rounded button looking things on the floor. Our original tank was a gal. and had gravel, a plastic plant and a small cylinder type air pump.
    How do we test the water(no one mentioned that aspect, either), and is there a test kit that tests for all the things one has to test for- if so, which one is it?
    And last but not least, what else? It seems like we were not informed of so many things about the keeping of the goldfish- We’re wondering how many other ‘surprises’ are coming down the pike? Really think people who give fish away to children ought to tell them the costs involved, and the things that need to be done for the fish BEFORE they hand these kids a ‘gift’.
    Thanks for your informative writings. You can answer me directly at atachaka at springsips dot com
    Laura & family

  38. avatar

    Hi Laura, I replied to your original comment on another blog post but I’ll repost my reply here in case you missed it…

    It sounds like there is a combination of things going on here.

    First, your tank needs to cycle. You can put the decorations and everything back in the tank during this period; they won’t affect it or vice versa. You can read more about this cycling process in our article on The Nitrogen Cycle.

    Our Goldfish Species Profile and Freshwater Aquarium Basics articles and our blog “How To Care For Carnival Fish” may help you as well. A 10-gallon tank is also small for goldfish with the high amounts of waste they produce. The “Carnival Goldfish” that are usually used as prizes like you mentioned are the same Comet Goldfish sold as pond fish and can grow up to almost a foot in length. Keeping a tank that small clean with those fish can be tricky and will need ample filtration.

    You mention that your tank came with a filter…what kind of filter and how powerful is it? I’m not sure what types of filters you are referring to by “floor gravel type”. When you mention “reverse-type system”, are you referring to the Reverse Osmosis Filtration mentioned in this article? That filtration system isn’t for on the tank; that is for filtering water out of the tap or other water source before use in your tank, similar to the Brita water filters or other filters used for drinking water (more details about that here). We have some information on Choosing An Aquarium Filter and the Best Aquarium Filters on our website. Filter size recommendations from manufacturers are generally very conservative and mased on lightly-stocked tanks. For a small 10-gallon tank with goldfish like yours, I would recommend a power filter or canister filter rated for at least 20-30 gallons.

    To test the water quality, you will need a test kit. The most important basics to test are Ammonia, Nitrite, Nitrate and pH. These four are like the “vital signs” of the aquarium hobby and are the most important to test when you see a problem. Goldfish tanks often have issues with Ammonia and pH with the amount of waste they produce so keeping an eye on these will be important. I would recommend getting test kits that use liquid drops rather than test strips; they are far more accurate and will last (and remain accurate) for much longer. You can get a Master Test Kit like this one or you can buy each individually. If you have any local pet stores or even swimming pool stores, they may test water for you as well…we test water at our retail store any time at no charge.

    Hope that helps…feel free to let us know if you have any more questions!

  39. avatar

    Hello, just moved to a 60 gal tank, hoping for filter advice. 10 goldfish incl 3 koi. All small. Biggest is common goldfish, about 4″ including tail. Still have the old HOB filter, supposedly good up to 50 gal, which maybe can supplement a new canister filter. Advice? Have been looking at Sunsun HW302, as we really can’t spend a lot, but some online advice has been that we need something more powerful for koi, even small ones. Also am very suspicious of the ceramic media these come with. Asked online and got the answer “it is smooth” and (ack!) some seem to be using it on the bottom of the filter to filter out large particulates. It’s supposed to have lots of surface area for nitrifying and denitrifying bacteria… but how can it if it’s “smooth”? Sounds useless to me. Should I buy my own media? And is that filter model good enough for 60 gal with 10 small goldfish? Thanks.

  40. avatar

    Hi Lisa, Unfortunately, that size tank is still far too small to keep those fish in permanently. Small goldfish and koi will eventually become big goldfish and koi and outgrow that tank. I wouldn’t recommend any more than 2-3 goldfish and no koi for that tank permanently. Common goldfish especially need a much larger volume. I’m not familiar with the specific filter you mentioned.

    For any goldfish aquarium, you would definitely want to go above the “recommended tank size”…those recommendations are usually for a lightly stocked tank, not for anything heavily stocked or with larger/high-waste-producing fish. For a 60-gallon, I would look for something at least 90-gallons or above. You can still use your HOB filter to supplement or for specialty media like ammonia-absorbing media or extra biological filtration media. A canister filter would be better for a tank that size and would give you a lot more options for media and setup. You can check out more options for filters in the articles on our website, The Best Aquarium Filters and Choosing an Aquarium Filter. We also have a number of general Aquarium Filter Guides on each type as well.

    I can’t speak to the ceramic rings specifically without knowing what type or brand they are. Many ceramic rings may appear smooth but are actually still pretty porous on a microscopic level and still give plenty of surface area for bacteria.

  41. avatar

    Thanks for the advice. I will check out those guides. This tank will not be permanent. We are moving up one step at a time. Right now, those little guys seem lost in the immensity of 60 gallons. Eventually we will have to move up to a bigger tank. We can do partial water changes every week very easily with a python hose thingy. And eventually, we will have to befriend someone with a koi/goldfish pond. Hopefully that is years away however. Do you know of the media called “biohome”? It is supposed to be absolutely the best, but if the ceramic rings that come with most canister filters are fine, I’ll stick with them. Thanks.

  42. avatar

    Hello Frank, one my way to pick up my 60 gallon tank for my 3 common goldfish. I just acquired them from someone who couldn’t keep them. One is approximately 3-4 inches & the other 2 are just a bit smaller than him.
    My question is about the pump, I am going to purchase the undergravel filtration system. Shall I get 2 and place them at each end of the tank? And what pump is the best in your opinion. Be as specific as possible. You know your stuff and I feel confident purchasing based on your suggestion.
    Any other tips? Kind of gravel? I know to put a thin layer… is 1 inch about right over the filter bed? I know they like to swim, so I don’t want to clog it up with a bunch of stuff, but what do they like, or what do you suggest for a tank that size? I am going to get some live plants as well for them to graze on, how many would you put in at one time? I’m also going to feed them pellets, which brand do you suggest?
    I know I’m asking A LOT of questions… I hope that’s ok. I just really want to do this right. I’m in it for the long haul.
    One of my fish came to me with the puffy cloudy white film over its eyes, which I’m sure was probably water quality, what can I do for him? They will be moved to the 60 gallon tank today or tomorrow, based on how long it needs to set up. Which leads me your my next question. Once I fill it and it’s to the 71 degrees that the other tank is now, can I just scoop them up and move them? Or do I need to let the new tank form good bacteria first?
    I think that’s all for now. Thank you so much in advance!! I know it’s a lot to answer, but hope hear back from you soon. It’d be amazing if I had these answers today. 🙂

  43. avatar

    Hi Kim, Frank is no longer with our blog but I would be happy to help you with your goldfish. You can also give our staff a call at 717-299-5691 to discuss your tank with one of our staff so we can make sure all of your questions are answered.

    In my experience, an undergravel filter isn’t the best choice for a goldfish tank, especially with common goldfish that get very large and produce a lot of waste. A more effective choice for the “long haul” would be a canister filter which would give you much more flexibility in filter media to help cope with the waste and ammonia produced by goldfish. I like and have used the Filstar XP-series myself but there are other brands out there that are very good with their own pro’s and con’s. Even a basic power filter or two will give you good flow and many have customizable cartridges that you can fill with media like carbon or zeolite to help keep the water quality safe for the fish. When choosing any filter, keep in mind that the recommended volumes are generally given for lightly-stocked tanks with small fish; for goldfish tanks, go up at least a size or two. For a 60-gallon goldfish tank, I would look for a filter rated at least for 75-90 gallons or more. You can visit our Article Archive for more information on Choosing An Aquarium Filter and other related topics.

    If you decide to use your undergravel filter, the best type of pump would depend on the type of undergravel filter you are using. Some need powerful internal pumps while others use only an air pump and airstone. I would recommend giving our Fish Supplies staff a call so they can help you make sure you get the best fit for the model you have. About an inch of most gravels is suitable but live plants and undergravel filters usually aren’t recommended sicne the roots can clog the filter. The plants would probably get uprooted and eaten before they have a chance to become too established but still may clog up the space used for filtration. The amount of plants added at a time isn’t too critical and would depend on the type of plants you are using.

    For the type of food…I would certainly recommend going with a Goldfish Food specifically. Hikari and Tetra are good brands.

    For the eye issues…if they were in poor water quality, improving that may help clear up the issue. Without knowing more about the water quality or seeing photos of the fish, it is difficult to diagnose it but it may clear up on its own once it is in a better environment. If it doesn’t start to improve within a few days or week in better water, feel free to email us some photos of the fish as well as water quality results (pH, Ammonia, Nitrite, Nitrate, temperature to start with) and I can try to give you a better course of action moving forward from there.

    For moving the fish into a new tank…any new tank needs something in it in order to establish the beneficial bacteria and all new fish should be acclimated to a new tank. If the fish were in a poor situation to start with, it would probably be best for them to get them into a better environment as soon as possible. You can add a bacteria supplement like Microbe-Lift Nite-Out II to help jump-start the Nitrogen Cycle cycling process in the tank. You would want to acclimate the fish to the new tank to give them a chance to get used to the new water quality as well as the temperature before adding them, just like you would when buying new fish from a store. You can view our recommended Acclimation Procedure on our website.

    If you have any other questions, feel free to let us know or give our staff a call at 717-299-5691.

  44. avatar

    Hello Frank, I have a 30 gallon tank and am currently using a Marineland bio-wheel filter of which the bio-wheel has never worked. I am having a major issue with algae. i AM FORCED TO DO A PARTIAL WATER CHANGE AND GRAVEL VACUUM EVERY WEEK TO WEEK AND A HALF. I too was concerned it was the food. I feed them pellets instead of flakes as I had read that may give them air bloat feeding from the surface. I would love to change filters and am very interested in the gravel filter would you please recommend what all I should purchase and brand name?
    I know my babies are crowded at the moment and will be purchasing a new larger aquarium in a few months, but for now they are in the 30 gallon till our kitchen remodel is over. That is their home and the only room large enough to house them on tile.
    I look forward to hearing your suggestions.

  45. avatar

    Hi Christine, Frank isn’t with our blog anymore but I’d be happy to help you out. First, I would want to address the cause of the algae. Algae is usually a symptom of another issue and without eliminating that issue, the algae won’t go away. Have you tested your water? For an algae problem, I would want to know at least the Nitrate and Phosphate levels since those can feed algae. How long do you have your lights on every day (including any bright ambient light from the room), what kind of lights are they and how old are they? Too much light (over about 8-10 hours) will definitely cause algae issues and old flourescent bulbs (over about 6-8 months) will start to degrade in light quality, giving you a more yellowish light that will promote some kinds of algae and cyanobacteria. Speaking of cyanobacteria…what does the algae look like? That will tell us a lot about what kind of algae (or “algae”) it is and the best way to get rid of it. Is the water itself green? Is it hairy algae or a thick slimy mat? A thicker mat would likely be Cyanobacteria which behaves much like algae but isn’t actually algae at all and needs different treatment to get rid of it. One more…how much water are you changing every time you do your weekly water changes? Changing too much water can “restart” an aquarium and cause certain kinds of algae blooms as the tank attempts to reestablish itself. If you’d like, you can email me photos of the algae you are seeing and I may be able to help you identify the cause of it that way. More details about the tank itself and the water parameter levels would help as well.

    For your filter question…Not many undergravel filters are available in the hobby anymore in favor of other filter types. The only undergravel filters that we still offer are the Lee’s Economy Undergravel Filters; the 29-gallon size would be the closest available for most 30-gallon tank but wouldn’t cover the entire bottom of the tank. In my experience, an undergravel filter isn’t the best choice for a goldfish tank. A more effective choice for the “long haul” would be a canister filter which would give you much more flexibility in filter media to help cope with the waste and ammonia produced by goldfish. I like and have used the Filstar XP-series myself but there are other brands out there that are very good with their own pro’s and con’s. Even a basic power filter or two will give you good flow and many have customizable cartridges that you can fill with media like carbon or zeolite to help keep the water quality safe for the fish. When choosing any filter, keep in mind that the recommended volumes are generally given for lightly-stocked tanks with small fish; for goldfish tanks, go up at least a size or two. If you know what size tank you are getting down the road after your remodel, go up a size or two from that to be able to use the new filter on the new tank.

    If you have any other questions or concerns, feel free to let me know. You can also call and speak with our Fish Room staff at 717-299-5691.

  46. avatar

    This is a very helpful blog! Perhaps you can help me with some advice, too? I have a 5 year old Oranda who is about 9 inches long from mouth to his beautiful double veil tail. He is in a 40 gallon tank. Three months ago, I added a 4 inch long Oranda, who is definitely growing. I do a 15% water change mid-week and a 25% water change each weekend. I am running three filters in this tank: two Aquaclear 50 gallon power filters (with the three layer filtration of sponge, charcoal and ammonia reducer) and an Aquatop 40 Filter with UV sterilizer. The larger Oranda has been lethargic and having mild symptoms of swimbladder disease. He is coming to the surface for air frequently or else is tucked into a corner, head down, behind a plant. I’ve been testing the water with the API kit and the ammonia and nitrates are both at unacceptable levels. I haven’t seen these levels since I cycled the tank two years ago. Today I did a 50% water change and added an API Bio Zorb Filter Media Pouch to the tank. My questions: Is there a more efficient filtration system I can use to keep water at healthy levels? I have all of the filters at one end of the tank. Should I upgrade to a 55 gallon tank? Would that be sufficient for two large Orandas long-term? (I feed my Oranda Hikari Oranda Gold, fresh vegetables, with tiny bits of shrimp or bloodworms. I had read that it might help to switch them to Hikari Baby Goldfish pellets as it might be better for Orandas prone to swimbladder?) Thank you!

  47. avatar

    Hello Maji, An upgraded tank is definitely a good idea with two goldfish that large. I would recommend upgrading to at least 55-gallons if not larger like a 75-gallon. With two water changes every week, it is also possible that too much of the bacteria has been removed and your tank needs to cycle again, especially after that 50% water change. The tank is essentially “new” at this point. Those three filters should be sufficient as long as the chemical media (carbon and “ammonia reducer” which I’m assuming is zeolite?) is changed regularly but hang-on power filters in general aren’t as efficient as canister filters. With goldfish, you would want to step up at least one size from the “recommended tank size” on the box; those sizes from the manufacturers are generally for lightly-stocked aquariums and can’t keep up with the waste that goldfish produce. You can also add a bacterial supplement like Microbe-Life Nite-Out II to help reestablish the aquarium. The behavior you witnessed is a common response to a water quality issue. Ammonia and Nitrite both affect the fish’s gills and gill function so they have difficulty breathing at high levels.

    If you need any more assistance or would like to discuss your specific tank in more detail, feel free to contact our Fish Room staff at 717-299-5691.

  48. avatar

    Dear Eileen,

    I really appreciate your detailed response and advice! I think a 75 gallon is probably the smartest choice because these two just keep growing! I’ll also research canister filters on your website. I didn’t realize that with two water changes per week, I have probably been too aggressive in using the gravel vac. and did remove too much of the beneficial bacteria. I’ll be more moderate with water changes, try the Microbe Life Nite Out and keep testing the water. Thank you again!

    Maji For

  49. avatar

    My goldfish’s fin is folding..when i bought, it wasn’t..is it because of current from canister filter?

  50. avatar

    Hello Seno, It isn’t likely that a filter would cause that but I would need a great deal more information about the tank to help you diagnose what might be wrong. Tank size, size of the goldfish and any other fish in the tank, and water parameters (Ammonia, Nitrite, Nitrate, pH to start with) would be helpful. You can also contact our Fish Room staff at 717-299-5691 to discuss the issue in more detail with one of our associates.

  51. avatar

    What powerheads should I buy for undergravel filter for my 90 gallon tank with 4 orandas?

  52. avatar

    Hello Ruth, I wouldn’t be able to give you any recommendations without knowing more about the filter…the brand and model, size, position in the tank, size of your tubing, etc.. I would recommend giving us a call at 717-299-5691 and speak with someone on our Fish Supplies staff (menu option 3) and they can help you figure out which powerhead might be right for your tank.

  53. avatar

    Hi y’all,
    Getting ready to set up a smaller tank for my fancy goldfish, 125 gallons. What filtration system would you choose if you could get anything you wanted? Obviously, I’m struggling with the power to move 1200 gph with low current . Please advise:)

  54. avatar

    Hi Denisa, You have pretty many options here. You could do a couple canister filters like the Fluval FX6 at either end of the tank or a wet/dry sump filter with multiple outputs to spread the flow. Either of those options would give you lots of flexibility for your filter media with plenty of flow. If you would like to discuss the options in more detail, feel free to give our store a call at 717-299-5691 and speak with one of our fish supply experts.

  55. avatar

    Hi there! thanks for sharing very helpful information! Could you give me some suggestions for quiet filter tanks? I’m running MarineLand Penguin filter for my 50 gal goldfish but it’s getting very noisy so I want to replace it.

  56. avatar

    Hi Bella, I would recommend looking at canister filters. They are more efficient and quieter than most power filters like the Penguin, especially for goldfish tanks. I would look at filters rated for at least 75 gallons or over for a 50-gallon goldfish tank since they are rather dirty, or getting two filters with a lower rating.

  57. avatar

    Thanks so much for your advice. I would consider this.

About Frank Indiviglio

Read other posts by

Being born with a deep interest in animals might seem unfortunate for a native Bronxite , but my family encouraged my interest and the menagerie that sprung from it. Jobs with pet stores and importers had me caring for a fantastic assortment of reptiles and amphibians. After a detour as a lawyer, I was hired as a Bronx Zoo animal keeper and was soon caring for gharials, goliath frogs, king cobras and everything in-between. Research has taken me in pursuit of anacondas, Orinoco crocodiles and other animals in locales ranging from Venezuela’s llanos to Tortuguero’s beaches. Now, after 20+ years with the Bronx Zoo, I am a consultant for several zoos and museums. I have spent time in Japan, and often exchange ideas with zoologists there. I have written books on salamanders, geckos and other “herps”, discussed reptile-keeping on television and presented papers at conferences. A Master’s Degree in biology has led to teaching opportunities. My work puts me in contact with thousands of hobbyists keeping an array of pets. Without fail, I have learned much from them and hope, dear readers, that you will be generous in sharing your thoughts on this blog and web site. For a complete biography of my experience click here.