Well I had finally gotten the temperature in the tank back down to a somewhat decent 79F (26C). I usually keep the tank at around 75F (24C), but I knew this was within recommended range for guppies so I was happy.

Unfortunatly, DANG HEATWAVE is back! We had a HUGE storm last night which cut out the power most of the night,,,, and you guessed it: with nothing to help the tank remain cool the temperatures soared up again,,, and is back at 86F (30C)!

Now I am very worried because one of my guppies is acting rather strangely today: she keeps either hidding in the plants, or remains at the bottom of the tank. She does swim around a bit when I appraoch the tank to take a look at her, but after a few minutes she'll settle down somewhere and just stay put. She looks perfectly fine physically: her gills look good, her fins are fine (and not clumped against her body), her colours are same as always (meaning absolutly beautiful :) ); I am at a lost as to what could be wrong.

Is it possible she is just stressed out because I have been having such trouble keeping the tank's temperature constant? If so, what can I do? Does anyone have any idea what could be wrong?

The heat and power outages are awful. It's supposed to go to 104 degrees F here today. Inside, as I type this at my table, the thermometer reads 84 degrees F. I took off my lab coat but have long pants per the company policy.

The heat can certainly cause lethargy in fish and make them act abnormally. I hope you can get the temperature down, and they should improve.

Have you tried ice cubes, maybe just a few or add some cool water.

Water changes with cooler water help a lot. If you want to use ice cubes, it's suggested to put them in a ziploc bag. For city water, this prevents the chlorine going in but even for people like myself who are on a well, the ice cube maker made add things to the water that you don't want (hey, I'm eating those ice cubes so that doesn't make sense?!).