I own a Tiger Oscar who is around 6 years old. I have personally owned him for 3 years. He shares his tank with a pleco, it is a 260 litre tank- well filtered, cleaned often ph ammonia, nitrate and nitrite levels have all been tested and all fine. For the past 5 days now he has not been eating, then yesterday I noticed his stomach/anus area is bloated and looks white...he was still acting his usual self other than not eating until tonight , now he is almost vertical- head down tail up just staying at the bottom of the tank. He swims occasionally and seems ok until he stops then his head goes down again.
Is there anything I can treat him with?