A must for tropical fish to keep the water the right temp.

Pros: easy to use

Cons: none

I've had a couple of these floating thermometers
and after a while the suction cups gets too limber and the thermometer just floats. That drives me nuts. Anyway, my heater does such a good job that
I don't use the thermometer all the time. You can
almost tell (once you've had a tank for a while) when
you need to check the temperature. For beginners, use it all the time! Fish like the water just right!

Pros: lets you know if water is too cool or too warm

Cons: none

Works great and have had forever but my thermometer always seems to be floating around the tank. I don't think the suction cup works well enough. Must have to regulate temperature and don't really care if attached or not.

Pros: easy to read, easy to put in tank, have forever

Cons: always seems to free floating