Digital thermometers, mercury thermometers, and other forms of thermometers can all be used in aquariums. Let’s start with a very affordable and basic digital thermometer like this one. Sometimes, such thermometers are simply allowed to float on the surface of the aquarium. Having a good thermometer to track your water's temperature at various times and days will help you identify and correct problems due to temperature changes. Depending on the species of fish, there may be varied temperature requirements as well. Here are some reviews of the best thermometers you can use: 1. In a mercury thermometer, the liquid inside is silver. A mercury aquarium thermometer or similar form of non-digital thermometer can often be attached to the inside of an aquarium with a suction cup. These little balls float on the alcohol and help you better see what temperature the tank is. Now is when you take a deep breath, because you have the alcohol model. Zacro LCD Digital Aquarium Thermometer Do a water change and remove all of the pieces of glass, and your fish should still love you. 6 Best Fish Tank Thermometers to Buy in 2020 1. Aquarium thermometers are a small but essential item for your aquarium. Top Fish Tank Thermometers Reviews. The silver liquid is Mercury and can be very dangerous to a fish. Yes, thermometers are required at household for more than just figuring out whether you are suffering from fever or not. So, you just released alcohol in a VERY tiny dose into your tank. It offers a 25mm X 12mm LCD screen, with a 1-meter cable connecting it to a … Older thermometers and some laboratory grade thermometers contain silver liquid. TOOGOO Digital LCD Thermometer. If the thermometer breaks then it will not harm the fish. To make your job easier, we have picked the best aquarium thermometers you can buy online right now. Alcohol models are dyed either red or blue. The silver or black balls or made out of the lead. A standard thermomater has mercury in it, ive no idea whats in an aquarium thermometer but i would play on the safe side and remove the axolotl and do a 100% water change. Although the tank may look fine, changing or unsuitable water temperature can have a negative effect on both fish and plants. If you have an aquarium at your home, then you will need to get yourself an aquarium thermometer because maintaining the right temperature of the tank water can be the difference between the life and death of your aquatic pets and plants. 1.