My fish is very bloated almost as bad as the one in the picture ptp posted. He isnt acting ill and peas and epsom salt havent helped. I think he has fatty liver disease or a tumor because it hasnt gone down in size but he has remained active and happy for months. If the bloat on your fish doesnt go down this could be a possible reason. If he seems lethargic like he isnt feeling well, he may have an infection. I think it is most likely constipation. This is very common in bettas. Dry foods expand in their stomachs and are harder for them to digest. I now feed my lil Stanley frozen brine shrimp, which he LOVES. They are largely made up of water and have fiber which both help him stay regular. If I were you I would treat him for constipation with 1tsp epsom salt (magnesium sulfate) per gallon. Do not use aq salt on your betta. Long term use can cause organ failure and immunity to the medicinal functions of the aq salt. I would only use aq salt in the case of external problems like fin rot or fungus. Bettas are not very tolerant of salt. Start out by fasting him for 2-3 days and see if his bloat goes down. If not, begin the epsom salt treatment if you havent already. It helps to relieve any buildup of fluid or food in his stomach. It has a laxative effect. epsom salt is safe for long term use if necessary but I dont think that will apply to you. Try feeding him half of a deshelled cooked pea twice a day. This also has a laxative effect as their bodies cannot digest this soluble fiber and it passes right through them. Peas will not give him the nutrients he needs however so try to find some frozen brine shrimp or daphnia at your local fish store to feed him. Once the bloating goes down you can alternate between frozen food and pellets. And fasting one day a week to help his digestive system rest. Also, try soaking his pellets in conditioned water before feeding them to him so that you will know exactly how much it will fill him up. Keep in mind that bettas stomachs are about the size of their eye so they dont need much food at all. It is better to underfeed than to overfeed! Good luck and don't worry too much. If it is constipation he should be better in no time.