* as usual, I used my hard-earned money to buy the product at the current price. In addition, I have nothing to do with anyone who may have made a penny in the purchase process. *. I'm just saying, I've had an aquarium for about 45 years. Under the right circumstances, this magnet thermometer is the best. This will make you wonder why no one has thought of it before. You can put it anywhere you want, and you can reposition it at will, and you can even move from one tank to another in a few seconds if you want. It's always where you put it last, and it's easy to see and read. In this respect, it is much better than the popular, cheap, convenient, discolored tape, which sticks to the outside of the tank like a piece of tape (it may also be more accurate than those tapes). It also defeats floating suckers that I can easily read but never find, or that, like 90% of all aquariums, never get stuck and fall to the bottom of the tank. I even prefer this thermometer to the fancy electronic digital thermometer, which needs an ugly and clumsy cable probe in the water tank. Don't we already have enough wires and hoses to untie? Remember, I said, "under the right circumstances." I put my Smarttemp thermometer in a 20-gallon tank and I use it to breed and raise babies, which is great. However, I guess the thicker the glass in the tank, the bigger the fish, the more grumpy the magnet will be.