So I found myself in a pinch two weekends ago. The outside A/C unit stopped working on a Friday afternoon. Temperatures outside were reaching 96 degrees Farenheit, and inside it was even hotter. I also found out that it's impossible to get someone out to work on an A/C unit on the weekend. No matter, I was able to repair it Tuesday the following week by replacing the capacitor which I had to order and get overnight shipped. Anyway, back to the real dilemma, my 29g tank was heating up, and fast. Since I don't have a reef, or reef lighting, I never worried about cooling the tank before, and therefore didn't have any cooling equipment.

In my despair, I came up with a way to cool the tank, it's a short-term solution and requires a bit of work, but it might save someone's fish, so here it is. I took ordinary ice from the freezer, and put it in a ziplock bag, I then floated the ziplock back in the tank. I also took three 1 quart mason jars and filled them with the saltwater from the tank and put them in the freezer. Every hour durring the day I would pour one into the tank, and refil it and put it back in the freezer for another 3 hours.

You might think doing this would change the temperature too fast and overly stress the fish. However, I found that in the 29g tank, the ice bags only lowered the temp by 1 degree per half hour, and the mason jars only lowered the temp by 1 degree (though that is quite instant).

The reason I put the ice in a bag is to keep the tap water from entering the sw tank and causing a bloom of diatoms or red slime algae. Don't worry about the sw in the mason jars freezing unless your freezer temperature is turned down much lower than it should be. Otherwise the salt in the water will keep the water from freezing.

Doing this, I was able to keep the tank at a "cool" 88 degrees Farenheit. Although that's still quite a bit higher than I normally keep the tank, it sure beat the 103 degrees that the house thermostat was reading. Hope this helps someone else in a pinch down the line.