I purchased to ensure the temperature in my Betta tank. I saw almost the same exact one at a local pet store for double the price. Its small, cheap and seems to work perfectly. I also have a floating thermometer in the same tank and the temps match.

They include an extra battery in the package.

I also use this to check the water temperature of water I am adding to the tank after water changes. The instant reading this thermometer gives are perfect for that task.

Probe has an accurate temp. The suction cups r worthless as everyone else stated. I just pulled them off and put velcro stips on. Their easier to manage than suction cups anyway. 4 stars cuz the company must be well aware of the suction problem and does nothing about it. Seller and amazon r great as always.

Works great and I love that it is easy to see the temperature whenever I need to. I keep it off until I want to read it, then turn it off again to save the battery life. The suction part for the outside reader doesn't really stick the best in my case but I just let it hang down on the outside of the tank and really doesn't interfere with anything. I am very happy with this little thermometer and I like that the part inside the tank doesn't take up hardly any room at all.

Received these for a vivarium setup. Both came with batteries already in them, an extra battery each, and were turned on showing degrees in C. Not sure for how long they were on, though it is possible they were accidentally turned on while in transit. The first one opened operated without a flaw, the slide feature to show F instead of C worked, and it matched temps with two other thermometers accurately. The second one, when switched to F from C, however, is in a constant fluctuation state between the two any time it is touched, jostled or looked at cross-eyed. Attempted to turn off then on again, switched the battery, and it still remains twitchy when showing F... so, I switched it back to C and turned it off for now. Obviously there's some sort of electrical issue with the F to C slide on that one which, disappointing, isn't that big a deal for me, but it may be to others. I would suggest getting a double pack or definitely more than one if you're going to purchase this thermometer just to be on the safe side that you don't end up with a twitchy one.

great little thermometer to use in my aquarium! i bought it after being skeptical of the thermometer sticker that was included with my aquarium kit. the screen is easy to read and everything was easy to set up. the suction cup w the actual thermometer probe is kind of useless because the probe is so light and can move around and the wire can actually go down further bc the probe and suction cup are attached like a bead on a string. nonetheless, the probe stays put and in the same place and the suction cup keeps it from floating way too far away. the wire is really long so i found that wrapping it and tying it with a rubber band helped keep it neat and hidden.