Certain foods can cause constipation. Unsoaked pellets. Bloodworms for example should be fed sparingly. Pellets should be soaked for about a minute before feeding so they expand before being ingested. Bettas have a very short digestive track that can become “blocked” easily. Overfeeding can also cause constipation. Siamese fighting fish should not be fed flakes. I feed my Betta fish a pea once a week and they love it and it helps prevent constipation.
Treat a constipated betta fish
Here are all the steps you should or may have to take. I’m including worst case scenario at the bottom, but constipation can be a “regular” occurrence and you shouldn’t have to go that far, but I just wanted you to have the knowledge just in case.
First, always do a partial water change (somewhere between 25 and 50% I’d say, depending on the tank size… it’s easy to do a 50% change in a 2.5 gallon, not so much in a 50 gallon) in case there is any infection. You’d be surprised what a water change can accomplish if things haven’t gotten too serious yet.
Feed your Betta a peeled pea. They may not eat it right away, but leave it in overnight and it will most likely be gone the next day. If not, remove it from the water so it does not foul the tank. I have a bag of frozen peas in the freezer, I take one out, put it in hot tap water for a quick minute and pop the pea out from it’s shell. It usually splits in half, which is fine. My Betta will wrestle with a half or whole and attack it with vigor.
Stop feeding your Betta other food for a few days.
Try feeding a peeled pea again in a day or two if it did not eat it the first time.
If you see significant bloat resulting in pine-coning of scales, this is unfortunately a bad sign, meaning your fish has Dropsy, a symptom of kidney failure. This is not usually treatable as there is no known cure once organ failure has occurred. If you have caught it very early, you can treat with an antibiotic which may cure the underlying infection causing the problem. I used Seachem Kanaplex, but did not unfortunately catch it early enough.
If there is significant bloating (with or without pine-coning), give your Betta an Epsom salt bath. You should NOT add the Epsom salts to the tank. Find a container (even a half gallon tupperware will do). In this example fill the tupperware with a half gallon of water from your tap and treat to remove Chlorine/Chloramine (you can use some tank water and some new water). Match the temp of the tank your Betta is in by filling the sink with several inches of HOT tap water, as hot as it will go. Put the filled tupperware in the sink. Add a tablespoon of Epsom Salts. Test the temp after a couple of minutes as the temp in the container should rise quickly. Stir to dissolve the salts. Do the same for a second container and put about a quarter tsp of salts in that one. Scoop your Betta out of it’s tank and place in the first container for 10 minutes, then move to the second container for 5 minutes and then place back into his/her tank (this method eases stress on your Betta). You can do this twice a day if they are not too stressed from the treatment after the first time. This should ease their swelling somewhat. If your Betta has Dropsy, you may want to consider euthanizing with Clove Oil after a few days. You will know when they are too miserable to put them through anything else.
Good luck with everything