I believe the fish in the oscar tank are stressed because the heater messed up and the tank went to at least 90 degress. I fixed that and lowered the water temp back to 80. Could that have killed off the bacteria? The 55gl temps dropped last night as of no heat and the heater stopped working for some reason. So I put a new heater in there. It was 74 this morning. Could this be the cause of stress. I will retest my tanks and post what I get.