i have a 13 inch red bellied pacu. hes very healthy no problems at all except with his tank i just cant seem to get the water to stay clear. hes the only fish in a 75 gallon tank. i have a magnum 350 canister filter with two bio wheels and an undergravel filter with 2 reverse flow power heads attached to it . he has plenty of air going to his tank and his light is only on for 9 hours a day. he doesnt get overfed as i watch how much and how often he eats, but the ammonia still skyrockets and its an established tank. i know hes a hearty fish and the ammonia doesnt affect him. ive done water changes and tried so many things to fix this problem. i know this is a piranah thread but they are cousins if anyone could help me id be very appreciative. i love my fish and i dont want to hurt him.