hi we have had 2 birstle nose plecos die in our 55 gallon tank. we baught a gold nugget pleco for the same tank and same thing happend. decided to get water tested nitrates and ammonia are fine. ph is a lil low at 6.6. we are naturally raising ph with coral. it is up to 7.0 on my last check. temperature is at 75 f. the other fish in the tank are doing fine. fire eel. peackock eel, barred spiny eel ( they are all babys and i know we will need to upgrade our tank once they get bigger) we also have a yoyo loach and 2 catfish. the other fish arent showing anysigns of stress or disease. our other tank is fine and has 2 plecos in there which are flourishing the only diffrence between the 2 tanks is the ph due to the diffrent substrates. does anyone know why the plecos in the 55 gallon would be dying?