need help keeping my tanks cool

[clowntrigger]

i need some help keeping my tanks cools during these hot days, yes we do have a few hot day here in Canada . i have been able to keep my tanks under 84 degress with lil clip on fans blowing into the sump. what i want to know is a way to have the fans only come on for example at above 80 degress and then turn back off it the temp of the tank drops below 80
also what tempature is bad i heard 85 plus things start to take harm