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Aquarium myths & Misconceptions

In the attempt to make aquarium keeping easier, or simply be able to provide some sort of answer to common questions. There have been a number of “rules” or guidelines that have found their way into the hobby, that you may have heard repeated over the years. You may have heard them from other hobbyists, from your LFS, Web Forums and even in published books and magazines.
I want to focus on a few that I feel really need to go away, that were either bad information to begin with, or have become obsolete. These myths and misconceptions have a far greater potential to cause problems for the beginning aquarist, than they are to provide guidance for success.

The Inch Per Gallon Rule


One 6 inch Oscar does not equal 6 1 inch Guppies

How many fish can I put in my aquarium? This is the oldest question in fish keeping, the first person to put fish in an aquarium asked himself this question. People want a number, they need a number, why can’t you give me a number!!!! Somewhere along the line, born out of the need to provide an answer, the Inch per gallon rule was conceived, and I hate it.
Why do I hate it? Because not all fish are created equal, and not all aquariums are created equal. Six one inch guppies do not equal one six inch Oscar. Body type, temperament, compatibility, adult size, diet and many other things should be considered when choosing fish. Slender bodies fishes, deep bodied fishes, schooling fish, colder water fish, all have different space and habitat needs.

Tank shape is also important, and is completely ignored in most cases. A tanks surface area (footprint) has much to do with how many fish it can easily hold. Gas exchange only occurs at the water surface, and is where an aquariums dissolved oxygen and carbon dioxide levels are maintained with the atmosphere. A tall narrow column shaped aquarium, will have a smaller surface area than an aquarium that is short, wide and long. Two aquariums can be the same size in volume, but be very different in shape and surface area.
This is a case where I don’t like the simple answer. My advice to people is to try and do a little research into the fish they’re interested in, see what they will get along with, and how big they will be as adults. Make sure you have adequate filtration, and take a conservative approach to stocking, don’t add all the fish at once. Most importantly, test your water quality, especially if you plan on keeping your aquarium near its limit. If at any point you are having trouble keeping your aquarium chemistry stable, do not add more fish, you may already have too many.

Fish will only grow to the size of the aquarium

fat-fish-little-tankThis one really bugs me, and I still hear it stated as fact on a regular basis. This is simply just not true, some fish may grow slower in a small aquarium, or can be kept smaller by limiting food, but this is not way to treat your fish. Often used in conjunction with the inch per gallon rule, to try and justify putting more fish in a small aquarium, by ignoring the adult size of the fish, this myth needs stop being perpetuated. Most fish that reach a large adult size, and going to get quite large in the first 2 years, if your aquarium is too small, don’t buy the fish. There are better choices to be made!

Small fish tanks are better for beginners.

There are a plethora of small aquarium kits on the market, many of the marketed for children, or with the entry level aquarist in mind. Where this has the potential for problems is when people confuse affordability and ease of setup, with the reality of the needs of a small aquarium. The downside of the small aquarium is how quickly problems can arise, conditions can change, and frustration takes over. Some of the things that can cause serious problems in small tanks, are common mistakes made by the beginner. Over feeding, overstocking, poor tank placement, improper heater and risk of contamination are just a few things that can have rapid and unfortunate effects on a small aquarium. Not to say these things are good for larger aquariums, just that they affect larger aquariums more slowly, and allow you a chance to correct issues before the results are disastrous. Be sure to check out our aquarium beginners guide before buying.

The dos and don’ts of cycling your aquarium.

This one could be a topic for a long article all by itself, so I will just hit on a few of bits of bad information that gets passed around to the unsuspecting new aquarist. Again, this is another topic where some simple research will go a long way to understanding the nitrogen cycle, and what to expect in your new aquarium.

Let your aquarium sit for a month before you start adding fish.

This is false; an aquarium is no more ready for fish after a month, than it is after 24 hrs. Once you have the aquarium setup, filters running, and heated to the proper temperature, you can start to add fish right away. 24 hrs is usually sufficient for your new tank to stabilize. Start with just a small number of hardy fish to get your system started.

Using a bacteria supplement will instantly cycle your aquarium and allow you to fully stock your aquarium immediately.

Although many manufactures’ of these products make them out to be a magic bullet, I feel Bacterial supplements should be used to complement the natural cycling process, not replace it. Without supplementation cycling will take 4-6 weeks, this time can be significantly reduced using supplements, but ultimately what is going to provide a stable aquarium is its own biological filter, the bacteria that colonizes and grows in your filter, and on your gravel, rocks and decorations. In a Marine aquarium, starting your aquarium with good cured Liverock will start you with a strong foundation.

Don’t do water changes while your aquarium is cycling.

This is also false. While your aquarium is cycling, toxic ammonia and nitrite levels can occur while the beneficial bacteria that consumes these waste products establishes in your system. You can absolutely perform small water changes to keep levels low enough that you do not reach levels that are toxic to your starter fish. While it is true that the first bacteria to colonize your aquarium are free in the water, especially if you are using bacterial supplements, the vast majority of bacteria that forms your biological filter lives on solid surfaces. Removing water will not affect this bacteria, and will not greatly inhibit your aquariums cycling ability. If you are a couple weeks into cycling your new aquarium, you should not be afraid to do water changes to help manage the high Ammonia or Nitrite levels.

Why is My Aquarium Water Cloudy?

We often receive questions about fixing cloudy water in a hobbyist’s aquarium or the water appearing to turn a different color. While not all environments have crystal-clear water and a slight tint to your tank isn’t necessarily a bad thing, water that is noticeably “tinted” or cloudy can be a symptom of an underlying issue in your aquarium. The color of the water can tend to point to a certain problem even if you haven’t yet tested the water quality. In fact, it may even be telling you what exactly you should test for next!

Why is my aquarium water green?

Planted TankThis is probably the most common and the simplest to diagnose. More often than not, green water is the sign of an algae bloom. Algae-eating fish or other critters won’t usually eat this type of algae. The algae, usually a single-celled form, is suspended in the water. The most common cause I see for these blooms in aquariums especially is high phosphate levels and this will be the first test I will always recommend. Phosphates come into the tank most often from the source water; if your water source is well water especially, phosphates may have leeched in through the soil or through nearby farms or gardens where fertilizers may have entered the groundwater. The phosphate levels may not be high enough to affect our health but in the aquarium, they can build up to levels where they are fertilizing the algae blooms and possibly causing other issues to sensitive fish and invertebrates. If you suspect this may be happening in your aquarium, grab a phosphate test kit to test both the aquarium and your source water. If the source water has phosphates, switch to a different source like RO (Reverse Osmosis) filtered water. Filter media can also help remove the phosphates already in the aquarium and regular small frequent water changes with phosphate-free water will help cut them down.

Another cause for green water may be lighting although this will affect algae on the surfaces of the aquarium as well as the water itself. If the lights on the aquarium are on for too long (over about 8-10 hours per day), this may be overfeeding the algae naturally in the water. Also, if the bulbs are older than about 6-8 months, the spectrum (“color”) of the light itself will degrade to a more yellowish color that isn’t as useful to healthy plants but will still feed the nuisance algae. Try decreasing the duration of the lights or getting new bulbs if either of those apply. If the bloom still hasn’t gotten better, test the phosphate!

Why is my aquarium water cloudy?

This is the other very common colored-water question. Usually, the water is white and milky. Whenever we hear this, the next question will always be “How long has this tank been set up with fish?” or “Have you restarted this tank lately (removed more than a third to a half of the water)?” A milky white cloudy water color to the water is a sign of a bacteria bloom which usually happens during the Nitrogen Cycle Cycling Process of a new tank or if a tank is becoming reestablished after a large water change, medication cycle or other event. This cloudiness will usually clear up on its own; try to resist the urge to do water changes since this will only make the Cycle last longer and take longer for the bacteria population that needs to grow to take care of this on its own. You can test the water during this time to make sure everything else is normal, keeping in mind that while a tank is Cycling, you may see spikes in Ammonia and Nitrite.

Why is my aquarium water yellow?

Yellowish water is usually simply dirty. This is usually a result of overcrowding or overfeeding and may also be a sign of harmfully high Ammonia and/or Nitrite levels. Test the water to see if this is the case and take a good look at the stocking levels of your tank compared to its size and filtration. If you have four goldfish in a 10 gallon aquarium, it is overcrowded and the waste they produce is polluting the water. If you have two large Oscars in a 55-gallon tank with one small power filter, it is overcrowded and underfiltered. Take a look at your feeding routine too; you may be feeding the tank more than it needs and the leftover food (or the waste the fish produce after pigging out) could be fouling up the water. To fix this cloudiness, consider getting a large tank or cutting back on the fish you have in it, invest in a larger, more powerful filter, and consider if you need to feed the fish less. A filter media with carbon or another chemical neutralizer can help remove the organics that are polluting the water as well.

Why is my aquarium water brown?

This one straddles a fine line. There are some environments known as “blackwater” systems where this is actually a good thing and completely natural. These environments are usually in forested areas without a lot of water flow. The leaves, wood and other organic matter in the water releases a substance known as tannic acid that dyes the water brown…this is the same thing that makes the tea you drink turn brown. Some fish that live in these environments actually need this kind of water chemistry and there are additives and materials available to help aquarists create this kind of system. If you don’t have these fish and don’t want a blackwater tank however, it can be an unsightly nuisance. This usually “accidentally” comes about from driftwood in the aquarium that hasn’t been properly pressure-treated or is too soft and replacing that wood will get rid of the source of the color. Carbon in the filter will help with this as well to remove the color and organics from the water. Keep a careful eye on the pH if you are seeing your water turn this tannic brown to make sure that the acids aren’t lowering your pH too far.

These are the most common questions we get about the color of the water in an aquarium. If you are seeing a different “color” or if the solutions here aren’t resolving the problem in your tank, give us a call or comment below and we’d be happy to help you figure it out!

For additional information – check out this article addressing a specific question from a That Fish Blog reader – Clearing Cloud Water.


Aquarium Decoration Ideas – Fish Bowl Designs & DIY

Our first blog on Do-It-Yourself aquarium decoration ideas seemed to get so many creative juices flowing that we’re back with some more ideas, tips and examples. In the first blog, we covered some general ideas for how to look at different objects as possible aquarium decorations. This time, we’re going to get more specific based on some of the most common questions from your fellow hobbyists. I created a few different looks after raiding my kitchen cabinets for inspiration using a 2-gallon glass aquarium and a 1-gallon glass bowl but you can adapt the same ideas to aquariums of any size.

Hershey Bears Betta Bowl

Hershey Bears Fish BowlI’m personally a huge hockey fan and have done an NHL Philadelphia Flyers-themed betta in the past using gravel and a plant in their colors. For this one, I kept it pretty simple and used a glass pint glass I had for our local AHL team and my personal favorite, the Hershey Bears, as well as some plant substrate in different shades of brown. Since the logo on the glass is pretty solid, I left the glass empty except for some substrate in the bottom. The glass is sitting on the bottom of the bowl itself and I added the substrate around it to keep it in place. Read More »

Natural Solutions to Common Freshwater Aquarium Infestations – Food for Thought

Trumpet SnailIf you’ve been an aquarium keeper for any significant length of time, you know that unexpected things can appear in your aquarium seemingly overnight. You may not know where they’ve come from, but suddenly you’re faced with overwhelming numbers of “alien” invaders in your tank, creeping, crawling and swimming all over.  Your immediate instinct may be to search for a quick chemical solution to eradicate the unsightly pests, but isn’t it safer for your fish and the aquarium habitat as a whole to solve the problem naturally? We discussed eliminating the causes of some of these critters as natural remedies in other articles, but this time we’ll take another approach…the possibility of finding and adding natural predators to the pest species you’re struggling with. It’s important to keep in mind that though these creatures have been effective in the tanks of other hobbyists, you can never predict the behavior of an individual fish and you may not get the results you’re looking for. Also remember that these fish have to be compatible with the habitat you’ve created and with the other fish in your tank…if you introduce any neew fish or invert to your tank, observe them closely to make sure all of your fish are getting along.


Whether you have live plants in your tank or not snails can appear in your tank and quickly boom in population. While they have their benefits as algae eaters and detritivores, they can become a nuisance if the numbers aren’t kept in check. Generally, for common snails we recommend botia loaches including Skunk Loaches, Clown Loaches and YoYo Loaches. These fish like to indulge on young snails and snail eggs, so they can get you ahead of the problem. However, they can be pugnacious and even a little aggressive in some cases, so they may not be a good idea in a tank with very small or docile fish.  True Siamese Flying Fox fish are another great solution, if you can find them in the trade.  If you’re plagued with Malaysian Trumpet Snails, your options may be more limited. These snails have much tougher shells than the common little snails that sneak in on live plants, and they can only be ripped out of the shell by specialized eaters with very strong mouthparts.   While the loaches may be able to handle very small Trumpet snails, larger versions will be too tough.  Some cichlids, including several Julidochromis species develop a taste and talent for eating snails, and C. rhodesii is also a known specialized feeder for trumpet snails. Read More »

How Diet, Lighting and Other Factors Can Influence The Appearance of Aquarium Fish

Red TerrorDedicated aquarists pour their hearts and souls into creating thier own versions of breathtaking aquatic displays. Countless hours are dedicated to precise placement of wood, rock and other ornaments, painstaking pruning of live plants, and,  of course, to testing and maintaining the water quality to provide the healthiest environment possible for the stars of the show: the fish! The ultimate goal is to have brilliant, beautiful, healthy fish to observe, and just about every other aspect of the tank contributes to the appearance of the livestock you keep. While the conditions that favor each species vary, you can provide the necessary factors to tweek the colors they show and make your fish look their best.

Understanding Fish Coloration

The inner layer of each fish’s skin contains color cells called chromatophores. Some chromatophores produce melanin, providing brown or black pigmentation. Some are capable of storing carotenoids which provide brilliant red, orange, and yellow pigments that come largely from foods the animals eat. Then there are iridophores, that contain crystalline deposits that reflect and bend light and giving the illusion of silvery, white, or metallic blue and green pigmentation. Read More »