Woke up this morning, early afternoon, to find my GBA breeding group (2 males and 3 females), their 20 plus babies and an Oto all dead, their bellies had exploded. The tank water was light brown and nothing seemed out of place. While trying to figure out what happened I touched the glass and it was bloody hot. The heater was still at 29 degrees, which it always was, but the actual temperature as 40 degrees as according to the thermometer. I'm guessing, which makes logical sense, that the heaters thermostat had broken and didn't stop heating