I have four cories in my 30 gallon, and I noticed a litle while ago that one of them would occasionally sit on the suction cup between the heater and the glass up near the top of the tank. Now I look and I see 3 of them doing this, two of them sitting on top of each other. Does this mean the temperature is too low in the tank or what? I've got it at around 76 degrees. Other than that, they're acting completely normal - if I scare them away from the heater, they go back to the bottom and do their regular cory thing.