Water temp @84 ........ thoughts?


New member
Ok My first summer with my new tank. I'm not a big fan of central air and my house usually hovers about 80 in the summer. With the halides beating down it hit 84 a few times. I've had the wife turn the air on so the room temp gets back down to 75 and that seems to keep the tank at 80ish.

Question is....

How warm can one go on a regular basis without hazards?

What are the reprocussions of have it at 82-84?

Does anyone normall run those temps? Expierence?

I'd rather not dish out $500 for a chiller jus for the fish. 220 gal total volume is alot to cool down just a couple degrees. It's Wisconsin and we have way more cool weather than warm.

Any input appreciated. Thanks!


Premium Member
Go buy a fan. Should put you where you need to be. I dont think 84 is harmful but I prefer not to go past 82


New member
Someone posted not to long ago a link to a study that was going on out on the reefs and it was showing that corals were growing very well in temperatures of 82-84 degrees. The only problem with your temp being stable at 84 if that is the case is you have a lot less margin for error if something did indeed cause your temp to spike any higher


Premium Member
Above 85 and you might experience issues...... A local reefer had his tank get above that (~90 degrees) and lost many of his corals....but not all.


Premium Member
84 is within the normal range for an "average" reef. It isn't a problem. Assuming they've been kept at under a normal temp regime (which most in the hobby aren't), most reef animals are fine up to ~90 for a day or two and many can go even warmer than that. Most can go a bit higher for shorter periods. 88 is pretty much where the danger zone starts though. Above that, some species will start to be affected. If you keep them under cooler or more stable conditions though, they will bleach at cooler temps.

Running the tank at 82 is roughly ideal. That's the yearly average temp for coral reefs around the world. Running a few degrees above that is no more dangerous than running a few degrees below it.

My tank regularly runs as high as 86 and rarely up to 88. It has even gone a bit above 90 for a few hours when the a/c pooped out. I've never had any temp related losses or bleaching.


Aquarist emeritus
if you're going to let it peak at 84, you may want to consider setting your heater(s) so it doesn't go below say 82 or 83. it's the temp swings that really hurt.

i know folks who do this in the summertime routinely (raise the temp range of the tank), i don't but there you have it.


New member


Mine goes up to 82-84 in our hot summer days in Montreal and everything goes on as usual....sometimes corals open a bit less but that's mostly it....I prefer when it stays below 82 but as I don't run a chiller nor an A/C it happens to spike for a while. I just put fans and it keep it not so bad. I also keep lights down somedays (when it hits 35 degrees C) :)

rj ripetide

New member
My tank goes up to 85-86 F with no problems. But that is on the high side for me. We had a prower outage last year and my tank hit 90F lost afew corals but most recovered in a few weeks.


New member
My tank varies in the summer time too. Having my tank in the garage, before the fan comes on in the morning, it's at 86. Once the fan comes on throughout the day, it cools down to 82 by lights out at night. I haven't seen any issues, but I only have softies (GSP, Muschrooms, Xenias, Zoas).

In the non-summer months, my tank stays around 78 to 80. If you need a cheap solution, the best is a ~6 inch fan blowing across the surface. You should net about a 3-5 degree drop without needing a chiller.


New member
You could turn off your heater since its summer time and also use a fan which can keep temps down. You could also have the AC turn on and maintain 79 degrees.

You could also have the lights come on during the night instead of during the day when its hot.

I've had my current tank that has lots of lps at 82-83 a few times and nothing happened. I will say this, my sps tank got to 84 and I had corals bleach on me. Just be careful and montior your tank.


New member
if you have a sump, put a fan blowing across the top, turn your heater's down to 78ish, and if need be, throw some RO/DI ice cubes in your sump as well. Keep an eye on your evap from the fan too.

On a side note,
greenbean36191 - Carmella Decesare is HOT!