My tank is usually between 83-85 but really this has been the hottest summer ever i can't remember it being this hot. I did have a chiller hooked up and i always had it set for 78 but the dam thing started leaking water all over the floor didnt notice until about 4 gallons were already on the floor. but yea the only problem i had was a few weeks ago the tank reached 91 (I was gone for 2 days the thermometer read 91) so who knows if it got hotter but 2 of my leathers and an acan were done and my cleaner shrimp was dead other then that no other problems. i love the summer but I am glad its almost over.