I have gone through two of these in the past, I really liked the idea of this small thermometer, and you can easily view it through the glass, but, about 2 or more months after I place it in my tank, they stop working, what I noticed is that they are not completely water tight, water ends up getting into the battery area and just destorys it, I have had the same exact thing happen to both of them I purchased, I thought maybe the first one was just bad in some way, so I bought another, made sure the back was screwed on tight so the gasket would seat properly, but then it happened again. I would say that it makes a good Temporary thermometer, really cheap so you could buy one and keep it around if your main one ever goes out, you could just pop this one in till a new one is purchased. In my opinion thats about all its good for!

JUNK. Bought 3. None read the same. One only lasted a month.