I have a nice little betta, have had him since October. He's very small and a plakat. Blue with yellow fins. I set up a 5 gallon with the idea that that would be his tank. Set up, cycled, put him in and it was clear from the beginning that the aquaclear filter I had on it was too much current for him. I kept messing with it but eventually tried him to a spare 2.5 gal with a built in mini filter in it and even then he had trouble. So I started just keeping him in the 5 sans filter (but with a heater) and doing lots of water changes. I know it's not ideal but every time I'd put a filter in the thing, he'd start getting all stressy and would have a hard time swimming. From the get-go I've thought something must be wrong with him. The other day he started having what looked like fin rot and trouble with his buoyancy. I did a full water change + aquarium salt +water conditioner and was pretty sure he wasn't going to make it. He would sink if he'd swim, tail down and would pretty much be vertical. If he'd land on the bottom, he'd tilt sideways a bit. I ended up moving him into a plastic cup and floating it in a tank with a heater that I kept from when I bought him. Honestly was just an attempt to get him close enough to the surface of the water so he could surface at all. When I netted him, he didn't move at all. I expected him to be dead the next morning. I got up, and he was fine and swimming around, eating great. Colors better.. I put him back in his tank with new water and for about 3 weeks with regular water changes. Fins were looking better too, I tried yet another filter and same problem with him not being able to swim at all. It was the smallest filter I could find and I put it on the 5 gal. After about 3 weeks of being much better, I woke up one day to find him lying on his side in the bottom of the tank again. He was curled up in a semi-circle and sinking veritcally again. Again, thought this was it. Put him back in the cup and then he was doing much better the next day. He's swimming now again and eating well. I still think his spine seems odd and he's still sinking a little bit. Color is looking better. I'm really stumped. Swim bladder problems, maybe? TB?