Fish do get constipated! It is a problem especially for laterally compressed fish and some fish species seem more prone to it, such as Goldfish and Bettas. It can also be caused by an improper diet, some manufactured fish foods, or overfeeding. Constipation can and will kill your fish if the blockage is not addressed.

Preventing Constipation

As it is with humans, roughage/fiber is important to avoiding fish constipation. Even carnivores get vegetation through the stomachs of the fish they consume in the wild, and roughage from bones and crustaceans. Make sure that your fish receives the appropriate amount of fiber/roughage in a form that is suitable for their dietary requirements. The amount required for good digestion depends on the fish, so some research is in order. Too much for the wrong fish or via the wrong source is also not good for their digestive system.

Carnivorous fish, as a general rule, do not digest vegetable fiber well and it is not required in high quantities due to a short digestive tract. According to’s Freshwater Fish Expert, Shirley Sharpe, a carnivore diet should contain less than 4% fiber. Not all fish ‘classed’ as Carnivores are created equal though, so research your particular fish. For example, many fish species classed as carnivores will also snack on algae or seaweed in the wild. This fact extends to terrestrial species in the order carnivora as well. The carnivora order contains more than 260 species, most of which are actually omnivores.

That being said, it should also be noted that seaweed and algae differ from terrestrial plants. They are low in carbohydrates and don’t present the various binding and anti-nutrient issues of terrestrial plants. This makes seaweed and algae a far more suitable form of dietary vegetation, even for obligate carnivores.

Herbivorous and Omnivorous fish require far more vegetation in their diet than Carnivores, some more so than others. It’s never a simple matter of half and half for omnivores. Most Mollies, for example, are omnivores that require a higher intake of vegetation than your average omnivorous tropical fish.

High protein diets without adequate vegetable fiber are going to be very difficult for a herbivorous (and many omnivorous) fish to process. Your veggie-loving fish have long digestive tracts and a diet with adequate fiber is required for efficient and optimum function. ‘Optimum’ being the operative word – some fish will appear to do just fine without any special dietary efforts, but that does not mean that their digestive system isn’t struggling to handle it, which can be an invisible source of stress.

For herbivorous and omnivorous fish, offset high meat protein meals with nutrient-dense high-fiber, low-medium carbohydrate meals. Avoid or limit high carbohydrate foods such as corn, sweet potato, parsnips and bananas.  Make sure your vegetable fish food is primarily vegetation (a label of ‘vegetable’ or ‘spirulina’ does not always mean that the product contains a high percentage of said vegetation).

Vegetable protein is an awesome form of protein for your herbivorous and omnivorous creatures, such as the protein in seaweed and peas. Vegetable protein offers efficient uptake & digestibility, with the uptake from seaweed and algae being far superior by comparison to any terrestrial plant.

Some high protein foods are notorious for causing constipation, especially Bloodworms. Be it the shape or the high protein & iron they contain, Bloodworms are best avoided for fish prone to constipation. They should be fed sparingly as a treat if you feed them at all, in my opinion.

Dr. Jim Greenwood of the Canterbury Veterinary Clinic suggests we avoid large imported bloodworms entirely, “A note of caution here on feeding the larger imported frozen bloodworm. These worms have a chitinous exoskeleton and numerous bristles that are indigestible for fishes with small intestinal apertures. The meaty portion of the worm is readily processed, but the hard bits remain and clog up the stomach in an immovable mass. Be careful not to feed your discus, rainbows and some tetras on the larger bloodworms.”

When you combine high protein with roughage, however, you can cover all of your digestive bases, leaving only the nutritional balance to concern yourself with.  Krill, shrimp and daphnia provide roughage with the protein.

You may wish to presoak foods to avoid constipation, especially super-hard pellet forms. There’s a happy medium there – soaking them too long may cause the food to lose its nutrient value. If you soak the food and it’s still hard & largely the same size after a reasonable amount of time, switch to another brand. Often in the desire to be stable in water, foods are difficult to consume and digest no matter how digestible the label claims the ingredients are. Likewise, if the food expands too much, feed very little as the fish will overeat and repent later. Freeze-dried or other whole dry foods should be briefly presoaked for fish who are particularly prone to constipation, especially surface feeders.

Internal parasites may also cause blockages, but that is another problem entirely. You can use preventative measures here too, however, by quarantining new fish and feeding foods with natural anti-parasite properties. The easiest way to accomplish the latter is to make your own fish food that includes anti-parasite ingredients, such as seaweed, calcium montmorillonite clay, and crushed garlic.  Note that the active component in garlic is allicin, which is heat sensitive. Since manufactured fish food is processed at high temperatures, the garlic in them does little good in this regard.

Fancy GoldfishToxic chemicals and fillers in some manufactured pet food are also suspected culprits of digestive issues in animals. We highly recommend limiting manufactured fish flakes and pellets in the diet of any fish and invertebrates, especially those with digestive issues. Alternatives include fresh, frozen, freeze-dried, low-processed or a homemade formulation.  Try to find a fish food brand that doesn’t use synthetic anti-oxidants (such as toxic ethoxyquin) or artificial coloring.


You may observe small or non-existent bowl movements, or hard, trailing feces. Passing undigested pellets are another indication that all is not well with your fish, be it a problem with digesting them or overfeeding. The fish may also bloat, which is often the first symptom a hobbyist notices. This may also cause erratic, uncontrolled swimming.

Unfortunately, the bloat that constipation causes will often be mistaken for a disease, such as ‘Dropsy’ (which is more a symptom of a disease than a disease itself). It can also include swim bladder symptoms as the blockages and swelling can impact the swim bladder, making the fish swim erratically. Hobbyists will often medicate for ‘Dropsy’ or ‘Swim Bladder Disease’, only to have problem worsen. The first step in any situation where a fish is bloated from an unknown cause should be to treat for constipation, unless there are other symptoms of disease.


Luckily you have two choices of treatment for constipation in fish, but the first steps are the same.

  1. Stop feeding (except for foods suggested below)
  2. Do an aquarium water change.
  3. Turn the aquarium heater up a degree or two.

Then use one or both of the following methods to remove the blockage:

Food Method: If the fish will eat, try feeding softened (barely cooked), pealed, quartered peas, or presoaked freeze-dried or fresh Daphnia. Chickweed may also be effective if you can get the fish to eat it.

Epsom Salts: If the fish won’t eat, treat the water with pharmaceutical-grade, organic Epsom Salts. You can also combine the two treatments if the fish seems to be worsening too quickly to wait for an outcome.

Some say you can just add the Epsom Salts to the tank and do a water change when the fish has a bowel movement. Others say it should be given in a bath. If the fish is in a quarantine tank I would leave it in the salts until they work, but not for more than 24 hours. The reason I say that is because I believe that moving the fish in and out of a bath is more stressful. You can also reduce the amount of Epsom Salts for a long term bath. If you don’t like that idea, place the fish in an Epsom Salt bath for about half an hour and then return him to his aquarium or quarantine tank. The standard recommended dosage for Epsom Salts is 1 tsp/gallon, but recommendations can vary too.


Once the blockage has been removed, resume feeding your fish in small amounts. Select easily digested (preferably whole) foods. You may wish to reevaluate the diet and make changes based on the natural feeding habits of your fish in the wild.

You should also provide a clean, calm environment to avoid stress-induced secondary infections.

When It Doesn’t Work

If the treatment for constipation does not work on your bloated fish, you are probably looking at one of two things:

  1. An internal injury or
  2. A bacterial infection

Unfortunately, successful treatment of either condition is rare. I have never had luck with antibiotics but you may want to try them. If so, be sure to treat in a quarantine tank and follow the directions on the package to the letter. Also be aware that many antibiotics will inadvertently kill beneficial bacteria in the aquarium, resulting in a new aquarium cycle.

If the fish does not seem to respond, you may consider humane euthanization. Hopefully it will not come to that and the odds are for you – the majority of bloat cases are, in fact, digestion related.

James Sales, Geert P.J. Janssens. Nutrient requirements of ornamental fish. Aquat. Living Resour. 16 (2003). Faculty of Veterinary Medicine, Belgium.
Carl D. Webster. Chhorn Lim. Nutrient Requirements and Feeding of Finfish in Aquaculture. Aquaculture Research Center, Kentucky State University, Frankfort, KY 2002.
Halver, J.E., Hardy, R.W. Fish Nutrition. Second ed. Academic Press, San Diego, CA, USA. 1989.
Winfree, Robert A. Nutrition and Feeding of Tropical Fish. Aquariology Fish Anatomy, Physiology, and Nutrition. First ed. Tetrapress, Morris Plains, NJ 1992.
Dreyer, Stephan. Feeding Tropical Fishes the Right way. TFH Publications. 1998.
Robert, Helen E. Fundamentals of Ornamental Fish HealthFundamentals of Ornamental Fish Health. 2009.

✔ You may also be interested in reading
Natural Prevention and Treatment of Aquarium Fish Parasites
Natural Fish Food for Fancy Fins
Live Fish Food Cultures for the Home Aquarium


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85 thoughts on “Natural Prevention and Treatment of Constipation / Bloat in Freshwater Fish ©

  1. The information on this site blows me away! I can tell you’ve been keeping fish for a long time and you’ve learned a lot along the way. Thank you for sharing what you know.

  2. I just love this site and the fish articles especially. I agree with everyone about the varied diet as long as it’s good for the species. It took me a long time to buy into human food for fish like vegetables but I sure see a difference now and they really like them. The more I learn the more healthy my fish and shrimp get and it’s thanks to people like you. Now I have so many I can sell some to support my fish addictions. 😉

  3. I guess we can tell from the volume of comments how hard it is to find fish information this great. I’ve stuck to my opinion that fish need variety im their diet no matter what the fish food companies say and they’re much more healthy than my friends fish who feed commercial food. That’s all I need to know to prove it.

  4. My fish get peas a couple of times each week but I didn’t know about the rest. They love the peas.

  5. This article is a great mix of proven info about fish feeding and new ideas coming from knowledge & experience. I agree we need more of that.

  6. +1 to the group with bloating bettas! Mine cannot handle any pellets or flakes.

  7. The cichlids were bloating often until I changed their diet, good aquarium advice.

  8. I’m working these suggestions into my fish care routine and already there’s a difference. They’re more active already and go crazy over the frozen fish food I got them with shrimp & spirulina.

  9. I had no idea about most of this information either!! I bet a ton of fishkeepers give their fish antibiotics that won’t do them any good.

  10. I’ll add my vote for a quality diet being the most important thing you can do to prevent fish bloat and constipation. That and frequent water changes are all it takes for really healthy fish and shrimp. when I started making my own fish food and dropping your Bottom Bites into the tank they all just took off, healthy and breeding like mad. I’m so thankful for your website & all I’ve learned from it!

  11. My goldfish has been fine lately but once he was constipated and almost died! Constipation seriously can kill fish! They need an appropriate diet because they can’t eat just any staple fish food.

  12. I agree the value of this post is in the preventative fish nutrition advice as much as the constipation treatments.

  13. I keep a lot of Gourami fish species and they can have bloat problems if they’re not fed an appropriate diet. I don’t know if it’s constipation or not but that would make sense because mine haven’t had a problem since I looked up their diet and stopped giving them fish pellets. Now they only eat crushed bottom bites, frozen brine and other frozen fish food. Sometimes I give them freezedried daphnia or mysis.

  14. I thought my betta had dropsy but I bet now it was constipation from the fish pellets. 🙁 I’m going to rethink the diet of my other bettas today.

  15. You know fish inside and out. I have to agree that this level of knowledge about domesticated animals is a rarity, especially from a blogger.

  16. My husband and I mix up our own fish food in a blender once a month or so. We started making our own after we almost lost our Oscar to HITH,,,,so much for pellets providing better nutrition to large fish. When we switched to homemade fish food his HITH cleared up and he hasn’t had it since.

  17. I had such a hard time with goldfish bloat that I stopped buying them. I love orandas and you have me thinking I can try again. Just a little more research into their diet and I’m hitting the LFS!

  18. I’m excited about making homemade fish food this weekend! I will probably spend more on fish groceries tomorrow than for my family!

  19. My bristlenose pleco got really sluggish and I hardly saw him for a long time. I was worried so I searched for information and found out I was feeding him WAY WAY too much protein. I went straight to the store and got him some algae food and ordered your veggie Bottom Bites. Now he’s one of my most visible and active bottom feeders! It’s astounding how much difference the right diet can make.

  20. a great writeup! fish or any pet will get constipated from improper diets like humans and they need variety.

  21. I was referred to this site by the folks at Advanced Aquarist for information about natural freshwater fish care. It’s great that you’re doing research on this topic, the hobby needs someone to focus on improving fish care and their diet.

  22. It wasn’t long before I learned to never feed pellets to my malawi cichlids because they gave them bloat. I asked my guy at the fish store and he said they never feed them pellets and tell hobbyists not to too. You bet they gained a loyal customer for their honesty.

  23. My fish absolutely go crazy when I put homemade fish food in my aquariums and they love frozen fish food & seaweed as well. Like others are saying,, they’ve never been healthier and I’m so glad I chucked the canned fish pellets. You are absolutely an authority on fish care and thanks for sharing your brain!

  24. Thank you!!! I didn’t realize that I should be examining wild fish diets but it makes so much sense.

  25. I crumble Bottom Bites for my Malawi babies and they grow fast and strong. The adult fish get a wide variety of fresh food and presoaked seaweed and I haven’t seen bloat in years. There simply isn’t a fish food on the shelf that is suitable for them because they’re special 😀 and they simply need real food.

  26. My fish were already in love with you because you make better food than I do 😉 Now I have no excuse and must try to make my own gelatin food for when they have worm tummy troubles. Thanks sweety!

  27. I’ve had problems with my malawi cichlids and bloat too. Some fish are just more sensitive to a lack of proper food than others so we have to do more research and be more careful.

  28. It makes so much sense but like Carol said we’ve been told that store fish food is all we need for so long we don’t question it.

  29. The only fish we have that get bloat are Malawi cichlids and it just breaks my heart when they die from it. It was like a light bulb when I read this and I’ll try your tips.

  30. So much about pet nutrition is logic but we’ve been conditioned to not think about it much. You’re changing that. 🙂

  31. You’ve inspired me to find more information about my fishes natural diet, I didn’t know how important it was but I understand now. I’m going to try making my own fish food too. Thanks a lot!

  32. I started researching dietary requirements of my fish when they refused to eat pellet fish food. I’ve never looked back! They’re more healthy and breed like crazy. Keep on educating the public and making Bottom Bites for those of us who want better food for our fish.

  33. I give my fish a lot of frozen fish food plus vegetables and your dehydrated food. I can’t believe I ever fed only flakes but I did! There’s so much to learn about diet but once you do you’ll have healthier fish. I could barely keep them alive before but I’ve won fish shows with these babies!

  34. It’s good to have this information in one place to reference instead of searching the internet to only find half as much. My aquariums take up a ton of time but researching fish takes even more. Trying to research fish food with all of the business hype makes it even harder. They have to sell their fish food but they don’t have to lie!

  35. I used to deal with constipation in fighting fish (bettas) quite often but it improved when I learned more about their diet. I wish they would tell us this information when we buy fish!

  36. You totally saved my betta! He couldn’t swim and was swollen up like a basket ball! I thought for sure he was a goner! I gave him a bath in epsom salts and today he is a new fish! I promise to spend the day researching the best diet for him because I never want to put either of us through that again! Thank you!

  37. I’m really enjoying this input, thank you so much. There are some very lucky (and perhaps spoiled 😉 ) fish out there!

  38. I feed my fish all kinds of food but it’s all either fresh or dehydrated. The fish are healthy and hardly ever sick. They love your Bottom Bites and they supply a wholesome variety of food and supplements that can’t be beat by anything else out there. They get them 3 or 4 times per week. They also gett bbs, grindle worms, sea weed, vegetables and frozen fish food.

  39. The only people who don’t say a variety of food is important for fish are the people who make fish food. When you share this kind of information it says a lot of good about you and how much you actually care about fish and hobbyists. Don’t ever sell out and keep up the innovation.

  40. You have no idea how happy I am to find this information for my goldies!!! I can enjoy my aquariums again!!!!

  41. I’d really like to read more information about tropical fish nutrition when you have time. Thank you.

  42. We need more of this kind of information. Fish have suffered at our hands long enough and constipation is just the beginning.

  43. i couldn’t agree more with mr. t! fish need a varied diet including fresh food like all animals. if we research like we’re supposed to we can provide much better care and avoid disease.

  44. I’ve lost two Betta fish to bloat or constipation and I hope now they’ll be the last! I loved those fish!

  45. Many people have no idea how to feed their fish or other pets because advertising has infused the general population with falsehoods.

  46. I have a goldfish that never did recover after a battle with bloat. 🙁 She still swims funny but she’s healthy so I don’t want to put her down.

  47. Google brought me here and I’m stayin! I’ve been keeping fish since I was 12 and I was selling mollies to aquarium stores by the time I was 14.

  48. I have goldfish AND betta fish and have seen fish bloat more times than I can count. Thank you very much for these natural remedies.

  49. I agree there are too many people jumping on the natural bandwagon making fish cures and food without any real knowledge. There have been several new fish food makers all over it and hobbyists are none the wiser because they think if it’s natural it must be OK. They’re using supplements, ingredients and procedures without any knowledge of how it can effect fish over the longterm. As you know there is a lot of study involved with healthy formulations but some people don’t care, they just want to make money off unsuspecting hobbyists. No wonder fish are constipated for gods sake! I’ll stick to bottom bites thank you because at least you have proven knowledge and are honest enough to admit it when you’re not sure about something.

    • I hear ya! There’s an entire system, from dietary balance to immunity to details like anti-nutrients and wild diet, that people need to understand before they have the expertise to care for one species, let alone provide products. No matter what good things a food contains, it’s all about balance for your particular fish. Whether it’s food, supplement or treatment, they need to have a full understanding of fish sciences before formulating and providing these products to others.

  50. You guys are too kind, thank you.

    I love seeing more natural pet care, including fish. It does frighten me to see some people formulating this or that without a clue of what they’re doing, however. Messing with people’s pets to make a buck is beneath unethical. Be careful out there!

  51. Just when I think I know it all you change the rules! 😕 But in a good way. It’s exciting to see natural pet remedies are being extended to fish and I can thinnk of nobody more qualified to make it happen. Good job Mel.

    • Writing an aquarium / fish related book is on my list of things to do before I die… but it’s a long list 😮 !

  52. I don’t have constipation issues with my guppies because I feed a variety of fish food like you suggest. As long as you meet all their needs it’s as simple as that for most common aquarium fish. Bettas can be tricky, true.

  53. Impressive to see good aquarist information like this on the internet. Your thriving fish are a testimonial to your health & nutrition knowledge. I enjoy the lack of BS too. I have to wonder about what you come up with sometimes but you always prove yourself in the end. Keep it up.

    • I have to wonder about some of the things I come up with sometimes too…LOL. They don’t always turn out well, but we have to keep trying to build a better fish. Something(s) sure has impacted aquarium fish health in a negative manner over the years. Natural diets and treatments are as good a place to start fixing fish as any.

      Thanks very much for chiming in. 🙂

  54. You’ve covered this thoroughly and brilliantly as usual. I get the feeling you wanted to write more about the nutrition part but ran out of room so I’ll be waiting for another post about that. Are all of the fish in the pictures yours? They’re real lookers, especially the livebearers.

    • Thanks for your kind words :-). I do find it difficult to briefly cover anything…LOL. I find that the desire to post short articles on blogs has riddled the Internet with superficial information on topics that really should be covered more thoroughly. Brevity is desirable to a point, but I like to research a topic and cover it fully.

      The fish are all from our aquariums. Livebearers are a definite fave! Visit for more info and discussion about Livebearers. I am the Community Manager there and also the Design/Photo Editor for the Livebearers Journal.

  55. I had problems with these when I fed only pellet fish food. Now I mix it up with frozen fish food, BBS and some freezedried stuff. That did the trick.

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