Hi their, its a 55 gallon, with 3 small oscars and a pleco. Last week the nitrite and nitrate was super high amonia near Zero i did 25% water change daily for 3 days in a row now water nitrite is 2.5, nitrate is 25 The other oscars had a kind of fungus which i treated with melifix,now they fine but the other oscar developed pop eye . Thanks!