A thermometer is a very basic equipment for an aquarium. However, it often overlooked. A thermometer measures the temperature of the water in the aquarium. The temperature is a very important parameter in an aquarium.
Fish are cold blooded animals which means that they cannot regulate their core temperature. Fish can die if they cannot tolerate the temperature.
There are many different types of aquarium thermometers available. Some models can be clamped to the aquarium walls. Others are of the floating type. There are models which measure the temperature and display them in an LCD screen.
More advanced models can measure the temperature and generate an alarm if the temperature increases or falls below specific limits.
In climates where there is seasonal changes in temperature, the temperature in the aquarium should be regulated. The Temperature can be regulated by means of aquarium heaters or coolers.