As you many have already figured out there are many things that you need to do when you set up your aquarium. Depending on which type of fish that you have in your aquarium will depend on the temperature of the water. One of the things that you will require for your aquariums is an aquarium heater. An aquarium heater is a small device that is placed on the inside of the aquarium that controls the temperature of the water. It is important that the temperature is set correctly so that your fish are kept comfortable.