what's your tank temp running at ?

[TheReefGeek]

We can't give exact numbers because it depends on the animals you are keeping, how quickly the swing in temperature happens, and also the accuracy of whatever device you are using to measure temperature could be off by a couple degrees potentially too.

If you are getting anything over 80, and it is a hot day and potentially getting hotter, I would play it safe and throw in a couple of frozen pop bottles. If your tank temp drops too much, your heaters will kick in. And install fans if you haven't already.

[Xtasia]

I wouldn't let it go higher than 83. 86 at the absolute highest.

If possible keep it within 3 degrees of your current temperature. Ocean temps do not change more than 1 degree a day apparently, so we should try to aim for stability. Any time you bring your temp down you won't want to do it too quick.

I've got my lights on a reverse cycle over the summer. They come on at 2am and go out at 10am. Actinics are on from 6-12 so that I can see the tank when I'm home from work. This way the hot MH lights are on at the coolest part of the day. My temp range is 77-80 using this method. So far, I haven't needed to use any other method to cool the tank.

You can also use fans, small water changes, and clean pop bottles of frozen RO to chill it. I've considered frozen cubes of Ro water for top off... holding it in the tank and letting it dissolve cube by cube.