Floating Glass Thermometer

I trust this glass thermometer. Digital thermometers are notorious for being precise but not accurate (e.g. they will tell you the temperature to a tenth of a degree but 2 degrees higher than reality). The suction cup works well to keep it in place in a readable position. The only thing I don’t love about it is that the “safe” range background is green, which makes it harder to read than the white part in the part I actually want to read.

I keep one of these gems in each of my 5 aquariums. Simple to use. Great price. Accurate reading

It's a nice little thermometer. It's great that it has the "green" range from 70 to 80 degrees as our tank is in my son's room and that means he doesn't even need to read the temp, he just needs to see if it's in the proper range.