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Bugs in My Aquarium? An Overview of Amphipods and Copepods

Please welcome back Desiree Leonard to That Fish Blog.

We as biologists at times take our knowledge for granted and forget that not everyone that is involved in the hobby is fully aware of all of the natural processes and progressions which occur in a saltwater aquarium. 
Frequently we are contacted by frantic new aquarists with the following:  “I have little bug – like things crawling all over the rock in my saltwater tank.  I swear they weren’t there before.  What are they and where did they come from? Are they going to make my fish sick?  How do I get rid of them?” 

Well, after talking the caller down off the ledge (so to speak), I give this answer:

In all likelihood, these are Amphipodamphipods and Copepods; shrimp-like crustaceans that dwell in the substrate and rocks.  Because of the thousands of species contained within these groups in Class Crustacea, I am not going into detail about the taxonomy of these organisms, but here are some basic facts about these tiny crustaceans.
• There are both pelagic (free swimming), and benthic (bottom dwelling) bugs.
• Copepods occur in all types of aquatic ecosystems; freshwater, estuarine (brackish) and marine.
• Amphipods are mostly found in marine ecosystems, but there are some freshwater and terrestrial species.
• They are just a few of the tiny animal organisms that make up zooplankton, which contributes to the overall make up of plankton.
• These creatures eat phytoplankton (tiny plants and algae that also help macopepodke up plankton), small microzooplankton (the division of zooplankton that are smaller than 200 microns, or 1/127th of an inch in size), and detritus.
• Only a few of the thousands of species of copepods and amphipods known are carnivorous or parasitic, and these are rarely found in a saltwater aquarium system.
• For many saltwater fish and other marine species, copepods and amphipods are a primary food source, both in nature and in captivity.
• Because these tiny organisms are a natural part of the plankton food chain in the ocean realm, they are naturally going to occur in a saltwater aquarium environment. They are also micro-cultured as food for various species of adult marine animals, as well as used and tested as a food source in the research of culturing and rearing all kinds of tank-raised fry.
• Copepods and amphipods most often appear in closed aquarium systems after live sand and/or rock has been added.  They will “bloom” in the tank when the temperature is slightly warmer and a food source is available.

isopodAnother critter that may be seen is the isopod.  Also called pill bugs, fish lice and rolly-pollies, these animals are found in all parts of the marine environment.  Most isopods are free living and harmless, feeding on detritus and algaes, however, some are predatory, or parasitic, and dangerous to other reef aquarium animals.

How did these “pods” get into the tank?  Well, they’ve most likely been there for a while, just not in numbers large enough to notice.  These organisms are microscopic or plankton sized when they start out, so until they grow large enough to be seen with the naked eye, you don’t know they are there.   They hitchhike in on live rock and sand, and it is only after you have placed it into your aquarium that these organisms crawl out and make themselves at home.

If you have a large population of “pods” naturally, count yourself among the lucky few.  Many aquarists go to great lengths to create a large healthy population in either their tank or refugium.  Remember, these “bugs” are a natural part of a healthy aquarium ecosystem, as well as an important food source required by some species to survive.  In most cases they won’t hurt anything.  You shouldn’t have to do anything about them.  If you are concerned however, you can provide a natural predator which should keep the population under control.  Here is a list of species which pick at live rock, or sift substrate in search of these tasty morsels.  Keep in mind those fish marked with a * are species which feed on these bugs as their primary food source.  They are challenging to keep, requiring a well established aquarium with a consistently high “pod” population to live on lest they starve.  Keeping more than one of these obligate “pod” eaters in a tank will most likely lead to a depleted food source.
• *Mandarinfishes/Dragonets; Synchiropus splendidus Blue/Psychadelic Mandarin, Synchiropus picturatus Green/Spotted Mandarin, Synchiropus stellatus Red Scooter/Starry Dragonet
• *Sand sifting gobies; Valenciennea spp. Sleeper Gobies, Signigobius biocellatus Twinspot/Signal Goby
• Most Firefishes are planktivores which may occasionally pick these bugs from the rock.
• Most Angel, Butterfly, Hawk, and Wrasse species spend their days grazing on fauna found on the rocks, however, do not consider this as a primary food source – merely an opportunistic treat.
• Seahorses feed primarily on these “pods” but are not a beginner fish and should not be housed with other fish.
Amphipods, copepods, and isopods are just a few of the fun little hitch-hikers we get questioned about, and we enjoy helping our customers with identification issues.  If you should have other fun things pop up in your ecosystem, here are some other things you can do to help identify them:
• Buy some good invertebrate identification books for your saltwater reference library.
• Refer to marine invertebrate database and profile information, as well as photo galleries.
• If you have a personal saltwater Web site, create something like a “Can You Help Identify This?” page. You can display photos here and allow visitors to email back to you about them.
• Post a message in various aquarist forums asking for help with identification. If possible include a photo of good clarity, or provide a link to a Web page you may have created as described above.

*Photo Emailing Tip: When you email a photo to another aquarist asking for help with identification on something, be kind. Only send an image that is reasonably sized, and is clear enough to tell what you want identified including a “brief” description.

Thanks,

Until Next Blog,

Desiree

51 comments

  1. avatar

    I have a reef tank, lots of healthy growing coral and only 3 fish (1 jaw fish and 2 clowns). I had a 75 gallon tank, without a refugium but upgraded about a month ago to a 125g with a refugium. I want to add a Mandarin, but I have no “bugs”. The small population I had seemed to have died off. How do I get the “bugs”. Can they be purchased?

  2. avatar

    Hi Desiree: Very informative piece of information. Now I can sleep in peace knowing that my tank it’s OK, thanks a lot and welcome back.

    Angel
    New York City

  3. avatar

    Hi Marc-
    Some LFS will offer the live “pods” by themselves, we unfortunately do not. Well cured live rock or rubble will have quite a number of these pods on them. The rubble that’s been buried in our bin for weeks may look bland but it’s usually crawling with all sorts of bugs.

    Another good way to introduce pods is with macro algae portions in your refugium. (which we do offer in our store) They will feed off the nutrients in the ‘fuge as well as the foods you are feeding your corals. As the population grows you can move them to the main tank by simply taking the algae and “shaking” them off into the tank.
    I hope this helps – good luck with your critter farm!
    -Desiree

  4. avatar

    Thank you sooo much, Now I can go to bed and not worry about my fish dying or these bugs taking over my house. these tiny little things were really getting in my nerves

  5. avatar

    I just was looking in my tank and saw the sand move.. as i looked closer I saw the little buggers that look just like the first drawing. At first I was worried, not I know its nature at work. And that is why I have a reef tank, to view nature. Thank you for all the info you provided!

  6. avatar

    You wrote a good article but what about us freshwater guys who have these “pods” in their tanks? unoccupied running established tanks.

    15g, flourite substrate ac20 x2 hob’s temp at 80.

    the flourite was rinsed for 4 hours and sealed the unused portion, can they live in 100% dehydrated environments?

  7. avatar

    It is quite uncommon to find “pods” in most freshwater aquariums, I can not say that in all my years as an aquarist that I have ever experienced them. I would not expect these animals to survive in a completely dry environment like a bag of flourite.

  8. avatar

    I got something in there, way too small for my digi cams. I have seen them thru an 60x scope and they are small, brown with spots almost cell structure like(science class) they float around the tank, no fins but swim with direction against current.

    Could uneaten frozen food hatch?
    daphnia and BBS are the only foods other then flake ever in the tank.
    flourite is new, tank was bleached out, no decor is the same, nor hardware, I hope I described them good enough to roughly diagnose, I cannt find anything online that resembled them.

  9. avatar

    It is very hard to say what they are without seeing them. I would not expect anything to hatch out of frozen food, although I guess it is not completely impossible. More likely that it came from a dry source, well water,or an egg laying insect that flew into the aquarium. They are most likely harmless, if you want to get rid of them you could treat for parasites, which will kill most any invertebrate in the aquarium.

  10. avatar

    I have a fresh water tank with these little cyclopoid copepods in it. Don’t know how they got there. I was pleased to know that I have a healthy tank, however, I don’t know which freshwater fish I can buy to help keep the population down. Please help.

  11. avatar

    Cynthia, most small fish will eat copepods, they are a vital part of the food chain in natural pond and river systems. I would that most Tetras, Barbs, Danio and others will eat them given the chance.

  12. avatar

    There are little, tiny, red dots swimming in my saltwater aquarium, and I just got it! I don’t know what they are. Can u tell me?

  13. avatar

    Lacey, it is hard to say what they are. Most likely, you have either a crab, or a shrimp, in the aquarium that has reproduced, and what you are seeing are the Larvae. They are most likely harmless. If you can take a photo of them, and email it to marinebio@thatpetplace.com, we would be happy to take a look, and try to help identify the little creatures.
    Dave

  14. avatar

    I just discovered I had copepods in my freshwater shrimp tank. I thought they were bugs and I was spazzing out until a long-time fish expert told me what they were. I pulled the moss from my stocked tank and tossed it in the shrimp tank and before long the moss was swarming with these things. Had I known what they were, I would have simply added some fish that would have eaten them. I bet my rainbowfish would have enjoyed that feast.

  15. avatar

    Live copepod cultures are coveted by some avid aquarists as a rich food source for many species. You’re a luck lady to have an established source. Thanks for sharing!

  16. avatar

    i have many of Amphipods and Copepods
    and some of them are relly big they about 1/4 ” or 3/8″ how big they grow ? , and also during the day i see them just some time but at night they all over , is the paper mint shrimp and the cleaner shrimp will eat them too ?

  17. avatar

    I’ve seen some pretty large ones, I would say they could reach 1/2 an inch in an aquarium. They are more active in the dark, hiding in darke recesses of the tank during the day. Peppermints and cleaner shrimp may eat a few, but the best eaters are small wrasses (halichoeres, and other small species like six lines, jewel wrasses, coris, ect) basslets and pseudochromis, gobies, and mandarins/scooterblennies. Many aquarists work to create well-populated bed of copepods just so they can keep mandarins an scooter blennies as that is there primary food source.

  18. avatar

    I have a 20 gallon tank a had a green terror and four gold fish on it , she put some eggs and after a few days seem like they hatch but it has been 25 days now a see a lot of micro organisms on my tank and they are multiplying really fast, I forgot to tell you that I took out the green terror and the gold fish that I had in the thank so they dont eat the babies but now I don’t know ir they are fish or something else

  19. avatar

    Probably not viable eggs if you only had one green terror, and you would be able to ID fry by now…usually if you see a lot of worms or other tiny organisms chances are they are feeding on the residual wastes and food (I assume you’re still feeding?), and with those fish in such a small tank, chances are there was aome organic build up before you removed the fish. The critters will have a population boom until the food and detritus is depleted.

  20. avatar

    how do i gain copepods i have a saltwater tank and want to pet a mandarin

  21. avatar

    if you have live rock and a well maintained tank, the copepods should appeat over time and establish populations. They can also be introduced on more live rock, live corals, live sand and live copepod cultures. Good Luck!

  22. avatar

    my friend and i found this bug which we are curious to know what it is. could you help us identify it? you can give me an email or something that i can send a picture to. thank you!

  23. avatar

    You can send the pic to marinebio@thatpetplace.com and we’ll see if we can help you out…was the bug in water?

  24. avatar

    Hi,

    I enjoyed your article, but I still have some concerns. I have two freshwater aquariums and I got a bloom of the amphipods identical to the one in the first picture. I thought there was only one but my substrate is full and it is in the smaller 10 Gal tank. I have a platy, 2 dwarf gouramis, 6 neon tetras and a tiny bristlenose pleco.

    What do they typically feed on and would they pose any danger at all to my fish? I do feed them every day (maybe too much apparently). Also would any of my fish eat these guys. The substrate is blue in this tank, making the amphipods easier to spot.

    P.S. I used to have ghost shrimp and CRS in the tank months ago? Could these be the next generation of shrimp? I would feel bad cause I flushed a few. lol.

  25. avatar

    It is possible that they are juvenile shrimp…if they are amphipods, they feed on detritus in the substrate and shouldn’t harm your fish. The fish may be able to eat some of the smaller ones, particularly the gouramis. If you’re worried about the population, consider cutting feedings to once every other day and/or siphoning the gravel more frequently. These can actually be a valuable food source for the fish, and they may feed more frequently on the bugs if fed less flake or pellet.

  26. avatar

    I have a 125 gallon tank with live sand and rock and I hate these things. I only have 2 fish in my tank a burfish and porcupine puffer and there are tons of these things in my tank. I used to have a tankful of fish but accidently killed every single one trying to get rid of these things. I’ve been considering getting rid of my sump, live rock, and sand switching to just using canister filters but my fish are such messy eaters, as soon as a crumb of food hits the bottom of my tank it is covered with these “pods” Any suggestions on at least minimizing the amount if not getting rid of them completely

  27. avatar

    The best thing to do is reduce feeding and vaccuum the sand bed frequently. They thrive on that extra food that falls to the bottom. If your puffers are not too large or aggressive you may also try wrasses, hawks or other predators that will feed on and reduce the copepod population.

  28. avatar
    Saltwater Aquarium

    Glad to know that there are service providers who is willing to help us in maintaining the saltwater aquarium. Thumbs up!!

  29. avatar

    Hi..I just read your blog & It was GREAT!!!.. I THOUGHT THAT I WAS THE ONLY AQUARIUM NUT. .LOL..But thank you very much for the information on this. .One question though. .. from the pictures of them. . Mine don’t look like any of those three. .. is there different pic’s out there. .??. Mine are white/clear. .. shrimp looking. .but they’re round in shape. .. at least my the time I see them. . Like they go round in shape when seen in cheeto and sand.. If you could direct me to the right place for that I would really appreciate your help! ! !lol. I like every living thing in there. .lol almost all. .;).. I lost my psychedelic Mandarin. .cuz I learned the hard way of the importance of feeding. .actually food not Prue “flake “.. (had someone else feeding while I was on vacation. .Ugh.. thanks for sharing this. . And listing too me rattle on..lol..thanks again. ..Alisa. …..

  30. avatar

    I have these littke white bugs they look like Very Little grains of rice. At first I thought it was just some alge but then I saw it was moving so I thought it was algea that gor disloged but the it was moving in the opposite diretion of the current. I can barley see them so they only look like moving grains of salt what are they, are they bad and how do you get rid of them (bugs creep me out. I have a 55gal with one black tail albino oscar a convict chiclid golden nugget pleco and a gibacept pleco thank

  31. avatar
    michael elliotson

    my pirhana ataccked me when i was cleaning his tank it jumped out at my face bit me and flopped on the ground it almost die and theres like a bug in the water and i dont know what to do i dont want my pirhana to die it was a 100 buck fish and when i cought him and put it him back in the tank he just keept on looking up where the lid was and he never attacks anyone i could put my hand beside him he wouldnt care than i noticed these bugs and got scared they are really small and i dont know what to do i belive there water fleas or a bug because i over feed altho i didnt over feed i give him 4 pelets a day or mabye its because i didnt git feeding fish so he can eat them i really need help?

  32. avatar

    if you have an oscar, chances are these are little scavenders feeding on excess detritus, leftover food and fish waste.They should not harm you fish, but it would be a good idea to cut back on feedings and be sure you vacuum your substrate when you do water changes to help remove the waste from the tank. They should disappear or at least become scarce if their food source is eliminated.

  33. avatar

    I’m a little confused about your comment…if the bugs that you’re seeing aren’t attached to the fish they are likely scavengers and not bothering the fish. There is a small possibility that you have some sort of parasite, perhaps fish lice, in which case you’ll want to treat the aquarium. Unfortunately, piranhas can be sensitive to parasitic meds, so be very careful with dosage and directions if you choose to treat. How large is the fish? I doubt that his behavior is being brought on by lack of food, and live foods are not necessary. You may offer frozen foods like krill or worms as an alternative. Be sure to test your water quality that may be a cotributing factor.

  34. avatar

    I have a 30 gallon tank with two 9 year old Parrot Cichlids. Today I noticed thousands of 0.5 mm white insects/crustaceans that were concentrated mostly in the clumps of algae that were growing just above the water line (on the plastic frame that supports the light fixture and the fake log where it was projecting an inch above the water). My fish seem unaffected and I do not see the little critters in the substrate or submerged anywhere in the water. In fact the ones that get accidentally swept into the water don’t look too happy. I took a decent picture but can’t figure out how to include that with this post. I mainly want to know if they pose any threat to my fish or if they are a warning sign that something is unbalanced in my tank. Any thoughts?

  35. avatar

    http://blogs.thatpetplace.com/thatfishblog/?p=4000 chances are they are a result of overfeeding and’or an abumdance of organic waste in the substrate and aquarium. Cut back on feeding and do a water change along with a thourough gravel siphon and the numbers should diminish

  36. avatar

    I have a regular 20 gallon fish tank not freshwater or saltwater with 5 mystery snails and a beautiful betta all of a sudden these little white bug looking things appeared they move around but seem to glide toward the walls of the tank they also crawl on the bottom of the tank all over the gravel since the gravel is white these bugs against it look dark but when they are swimming or on the glass they look white I have no idea if they are good or bad for the tank also too they seem to be fine with the light being on for my tank since I see alot of ppl saying these critters don’t like light and they hide also I see a worm looking thing it’s white just coiled up against the glass one end is attached to the wall of the glass and the other end is kind coiled and it just sits there like that can you let me know if this worm thing is safe or not I also see alot of ppl saying these things are in their tanks but they have saltwater or freshwater so how is it I have these critters if my tank is just a regular tank

  37. avatar

    Chances are they are the result of overfeeding your tank. Reduce the number of feedings and the amount of food, and be sure to vaccuum the gravel when you do your water changes. Once you get the overfeeding under control and the substrate cleaned up, the critters you see will decline in number or disappear completely. They are simply scavengers feeding on detritus and waste.

  38. avatar

    Actually I feed them once a day and that’s in the morning when I wake up and yes I make sure I don’t over feed them so it’s not that and I don’t have a vaccum thing for my tank and can’t get one I do change the water once a week I recently got a couple of dwarf frogs which happen to eat the pods and a loach as well but the pods still seem to be growing more which is frustrating I am just gonna have to get algea remover and they will be gone since they are an algea anyway

  39. avatar

    I go a 90 gal saltwater tank and I have no fish in my tank at the moment( all my fish died i think the pet store ant doing a good on selling healthy fish) but there is a crab and two camel shrimp and some snails I have noticed small white all most see-through is this bad or good ? Can you let me know?

  40. avatar

    Justin, most likely what you are seeing is nothing to be concerned about, and you are only now seeing them because there are no fish in your aquarium to eat them. It is hard to say what they are exactly, if you can take a picture and email it to fish@thatpetplace.com we will do our best to try and ID the critters that you are seeing.

  41. avatar

    When I had my saltwater 30 gallon set up fluval 206 whole set up was sweet what i discovered is u turn ur lights off at night whatever ur normal time is in about an hour or long as possible come back to our tank w a flash light n go over your whole take check ur live rock. I promise u will find so many pods different speices well don’t Ifind iIhad a small issue wwith bristle worms never touch them barehanded u will be irritated for a few days Isome larger ones too 9% of that cool stuff hitchickes into uour tanks not much u can do as long as its nothing that’s gna infest your tank n harm fish n whatnot . Leave them part of the ecosystem u brought in. That’s my personal opinion been collecting n taking care of all kinds over 20 years got my fiisrt tank at 10 been addicted since! P.s. love your store. Awesome!!

  42. avatar

    Eric, I would encourage anyone who keeps a reef tank to check it out after dark, it is amazing to see what you never knew was living in your tank.

  43. avatar

    My 75 has been set up for 10 years with around 200lbs of premium live rock. I have millions of tiny little buggers of different shapes and sizes I stock my tank with tiger pods once a month to keep my 6 line happy and to help keep my tank clean leftover food doesn’t last long and they don’t bother the fish.

  44. avatar

    Hi all. I’m new to salt water tank. I have a 75gl setup, plenty of live rock. My friend gave me some live rock and I noticed these brown plants living on a few new rocks. I’ve been trying to look it up but no answers. Does anyone know and are they harmful. I’m shooting for a reef tank now. Thanks

  45. avatar

    Hi Manny, If you can take a photo of the “brown plants” and send it to us, that would help us to try to ID it for you. Without knowing what you are referring to, we can’t say if it is harmful or not. You can email our marine biologists with your photos attached at fish@thatpetplace.com.

  46. avatar

    There are little bugs or some thing swimming around my freshwater fish tank. These things are flashing a green light and they are really small. The fish are eating them, please help me

  47. avatar

    Torrey, hard to say what you are looking at. If you can get a picture of the little critters, email them to fish@thatpetplace.com, and we would be happy to try an figure out what you have in your aquarium.
    Dave

  48. avatar

    I have a salt water tank with about even coral, a hermit crab, and one fish. There is a ton of these little white bugs and I don’t know what they are and how to get them safely removed. Could you help please?
    Thanks

  49. avatar

    Hello Kaelyn, We wouldn’t be able to say with any certainty what you have without seeing it. It is likely that what you have are the copepods and amphipods discussed in this blog. They aren’t harmful and many fish will eat them. If you’d like, you can take a photo of what you are seeing and send it to fish@thatpetplace.com and we can see if we can identify them any better.

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