my dat was sick about 2 weeks ago so i isolated him in one part of the tank. i treated the tank with prrrr..... (a liquid against parasites) he was doing better but 3 days ago he started just laying on his side , breathing normally but still on his side at the bottom of the tank, he is eating but when he goes to get the food he swims but instantly sinks like a rock , what do i do about that how can i help him ? i don't want to kill him. I'm just hoping he will get better on his own.....