As you"ll have already figured out there are several things that you just need to do once you set up your fish tank. depending on which kind of fish you have in your fish tank can depend on the temperature of the water. one of the items that you will require for your fish tanks is an aquarium heater. a fish tank heater is a little device that"s placed on the within of the fish tank that controls the temperature of the water. it"s necessary that the temperature is set correctly so your fish are kept comfortable.