I've had this halfmoon male betta (Triton) for about 3-4 months. I got him from Petsmart and upon receiving him he had some breathing/swim bladder issues. I treated him in a 1g tank for a few weeks with a little dropper of Betta Ultimate made by Hikari. He responded really well to it, his breathing evened and he began swimming well and eating regularly. He was later moved into a divided 10g with my show plakat male and he did really well. I kept him on the side without the filter as I didn't want to stress him when he already had experienced swimming issues. He seemed well. He ate regularly and swam well; though not as active as my other three. Then he somehow got passed the divider and he and Pallaton (show plakat) proceeded to fight. It was very brief as I separated them quickly. Pallaton seemed kind of hyped up for a while and Triton wouldn't eat and barely swam. So, I cleaned out both of my 10gs and he was put with one of my veiltails (Hermes). Immediately after the switch he was lively and began eating again, even swimming more than he had since I'd gotten him. But everything went down hill on the trip down south after the semester ended. It seems to have stressed him out and he now has quite a giant bulge near his caudal fin. I believed it was SBD and treated him for that, but he's had no change. He was isolated in my hospital tank (1g) and treated with aquarium salt, daily water changes, and fasting. I read somewhere that feeding him a pea would clear out his system if it was caused by constipation, but that didn't work. I thought it might be a parasite or a bacterial infection so I treated him for a week with PimaFix. He still has had no change. I'm at my wits end with how to help this little guy.
He is currently in a heated 5g tank on his own - the temperature has been kept at 76-78 with the heater. The filter is a tetra whisper and is fairly mild. He remains on his side at the surface most of his time if he doesn't squirm to a corner and prop himself to stay upright. I've been feeding all my bettas New Life Spectrum with frozen bloodworms and brine shrimp as supplements. I feed them twice a day except for Saturdays - when they are fasted. I was feeding them freeze dried foods until I realized that can cause constipation, so I have strayed from those.
I have some pictures of him so you can see the bulge. Otherwise, he doesn't seem to have anything wrong with him that I can see, health wise. But, I'm also not an expert.
Any help you guys can give me will be greatly appreciated. I just want to help him, he seems so miserable.