i have a 2 year old betta fish who has always been very healthy but recently he has been laying at the bottom of the tank, seems like he has an extremely difficult time getting to the surface to breathe, lately he has been almost sitting upright on his tail with nose up, barely eating anything. his fins look ok, and the other bettas i have are doing well. he has no visible parasites, ick, bloat, dropsy, or rot. i have lowered the water level so he doesnt have to work so hard to get to the top, and am changing his water about 2x a week to compensate for the decreased volume. what else can i do? ive used a bit of melafix, aquarisol, and pinch of sea salt, none seeming to help. he was one of my first fish, and one of my favorites. help!