Its been very warm here in IA last couple weeks and my tank has been at 82. no one showing any stress yet. It usually hovers around 79. I have a cheap walmart fan blowing across top of tank and that helps alot- it would be about 86 without it! You could try that if you are concerned- but watch your evap rate- it will increase quite a bit!
I used to have money till I set up my reef.... Now all I have is a major addiction to reefing!