It’s approaching 90 degrees here in Los Angeles. I have no air conditioning in my apartment. Thus, my freshwater aquarium is getting way too hot for my poor fish. I’ve turned off the hood lamp, and I’ve got a fan pointed at it, but it’s still several degrees above the safe zone.
My question is, can I do a partial water change, replacing the water with fresh water that’s a few degrees below what it should normally be, in an attempt to lower the temprature to normal? Or would this shock the fish? If this isn’t a good idea, can anyone suggest anything else?
The fan is a good idea. Evaporative cooling & all that. Yes, you can do partial water change too. People always say sudden temp changes are bad for fish but they experience sudden temp changes in rivers & lakes all the time. Bogus, I say, as long as it’s not too drastic a change & the fish are otherwise healthy.
You might increase water circulation too. Warm water holds less oxygen than cooler water so your fish could use more O2 right now I’d bet.
What kind of fish? Salt water or fresh?
In my opinion you should add a few icecubes every half hour (or at faster rate for larger aquariums.Because ice melts fairly slow it is not a shock to the fish. I have a 10 gallon freshwater aquarium and have used this technique with 100% success. leave your filter and bubbler on to circulate water and temperature.
I second the ice suggestion, but would suggest placing the ice into a ziplock bag and floating it in your aquarioum rather than releasing the cubes directly into the water, just in case your water has chloramines in it (since I doubt you treated it with Amquel before you froze it!).
I have a 37 gallon tank full of goldfish and a pleco. These are both very hardy fish and handle fluctuations in temperature as well as straight tap water.
When the H2O temp gets around 90 degrees, I still like to drop a jug of ice in the tank with them. This does not drop the temp as much or a fast as doing a partial H2O change with H2O straight out of the hose.
Thanks for the ideas! It’s a 20-gallon freshwater tank, and there are several zebra danios, a pleco, and an aquatic frog (I’m not sure of the exact species of the aquatic frog, to be honest). It’s the frog I’m the most worried about. All the others seem to be acting normal, but the frog, which normally spends most of his time at the bottom of the tank, hiding amongst the plants with only occasional forays to the surface, is now spending all day swimming around the top of the water. At first I thought he was dead, but he’s not.
I thought about ice cubes, but didn’t because I was worried about the quality of the water. No, I don’t generally treat my water before I freeze them into cubes! Floating them in a plastic bag hadn’t occured to me. I will try that. I’ll also increase the circulation, as levdrakon suggests.
Well, on my 90 gallon (saltwater) reef tank, I use a 1/4 hp chiller. They run with a compressor like a refridgerator or air conditioner. That’s overkill for your little freshwater tank, and they suck up the juice. (electricity bill-wise).
If you go the ice cube route, you might consider freezing water in milk jugs instead.
What I would do in your situation, however, would be to buy one of those IceProbe Thermoelectric Aquarium Chillers. They use thermoelectric technology - ie. plug them in and one side gets hot, the other side gets cold. They only draw about 40 watts and should drop 20 gallons by about 4 degrees.
I wouldn’t bother with the ice or the water changes. The ice probably wouldn’t cool the water as much as you think, and the water changes could shock the fish and would eventually screw with the water chemistry if done too often. And in either case the water is just going to heat back up.
What you should do is:
Make sure the tank is out of direct sun.
Leave the lights off.
Remove the cover, and put a screen over the top if your fish are jumpers.
Have a fan blowing air over the top of the tank.
More things you could do:
Have an airstone running. The bubbles rise and disturb the surface of the water, allowing more oxygen to dissolve in the water.
I see you have Zebra Danios, those fish are commonly used to condition new tanks because they are so tough. The only time I’ve had a Danio die is when a bigger fish decided to take a bite out of one!
Once you do get your aquarium cooled down (via whatever fashion), you can insulate it with styrofoam to keep it cooled down somewhat. (You can get styrofoam insulation at Home Depot, Lowe’s, etc.) It’s not the most attractive or convenient solution, but if it’s only for a few days …
90 degrees is pretty hot for most freshwater fish.
ARGH! Danios are cute little gregarious egg-laying schooling fishes that are quite entertainingly promiscuous when happy. Decidedly not for “conditioning” new tanks. :mad: 
It’s 90 degrees outside; the tank isn’t that bad. It’s only about 84 degrees in there. Not at emergency levels yet, I don’t think, just high enough for me to be concerned. Thanks for the insulation idea, though!
Erm… I actually did start up my tank with them. Sorry to make you angry! They are good fish. I like 'em.
I’ve seen a person use two empty pop bottles full of ice to keep a 20 gal tank cool. Have one in the freezer, the other in the tank. When it thaws (or the temp is too high), switch it with the frozen one - you can just fill it with tank water so as to not worry about getting extra chlorine from tap water in the tank… just leave the cap off both in the freezer and tank.