Review on VIVOSUN 2-Pack LCD Digital Aquarium Thermometer Fish Tank Water Terrarium Temperature Gauge with Suction Cup for Turtles by Allison Carpenter

First of all these thermometers were shipped already switched on although they have not been opened and do not appear to have been tampered with. There was supposed to be a plastic tab in the battery compartment that had to be pulled out, but there isn't. They also fluctuated constantly, reading different ambient temperatures from each other. It was the same when I put them in the same bucket of water. The suction cup on one was terrible, no matter what I tried it refused to stick. In the end I glued it to the glass. To be honest I don't know why I put them in my tanks, I just don't feel like returning them. I have heaters in my tanks with a rough estimate of the temperature, I just wanted something more specific to double check but it's not! The temperature shown is probably wrong, but shows fluctuations (e.g. last night I was covered up for a while and the thermometer showed a drop). Also, they're cheap and I don't trust them, so they're pretty much useless. Bottom line: you get what you pay for. If you want close reading, spend a little more and get something better.