We had some in the old bio lab when I was in college, neat critters just to have on display.
Anyhoo some cooling techniques since we've dealt with 100+ degree weeks here in MN this summer, and we didn't even have air conditioning for most of it:
1) BASEMENT. The main floor hit 98, but the basement was 80.
2) HEAT OF EVAPORATION.
If I remember my science correctly, 1 calorie (small calorie) is the amount of heat needed to raise 1g of water by 1*C.
The heat of vaporization of water is something like 500 calories per gram. That should mean that if you evaporate an amount of water, cool 500 times that much water by 1 degree.
A fan blowing across a wide area of water should help a lot, especially if your indoor humidity is low.
3) HEAT OF FUSION
Fill empty bottles with water. Freeze in freezer. Place in water. The heat of fusion (heat required to melt ice or be taken out to freeze water) is still pretty high at something like 80 cal/g. Once your water bottles are melted, re-freeze them.
These are tips to survive the heat, and may or may not be suitable as long-term every-day solutions year round, depending on how much work you like to put into it.
4) NOT EFFECTIVE: CHANGING WATER
I just figured I'd throw this out there, but changing out your room-temp water with colder tap water is very temporary, and it will adjust in temperature fast, as it only takes 1 cal to raise 1g of water 1*C. Not only that, but I bet Axolotls don't like chlorinated tap water.