JW - Fusion Smart Temp Thermometer
The Fusion Smart Temp Thermometer uses a magnet to say put on the glass instead of a suction cup. It can read temperatures from 30 degrees F to 100 degrees F (0 to 40 C).
Rivers to Reef says: Suction cup thermometers can fall off the glass a lot once their suction cup gets old. These are held on by a magnet, so you wont have to worry about that. We also prefer in tank thermometers to the ones on the outside, as they tend to read water temperature more quickly and accurately.