So far I have not had a problem... during the day my tank his a high of 81.2, and at night it drops to 79.6... some reason I have two fans running and I can not get to cooler then that. I am not not running a thermometer in the tank right now either. I have it turned off or down to 54 degrees as of right now...
This should be interesting when I have to kick the AC on if it get warm enough here... but for now I'm just watching it and everything seems to be thriving just fine.. I have zoa's, nem's, 4 fish, snails, and assortment of hammers and other corals. This tank has been running like this now for about 8 months.