It all depends on the size and type of your aquarium and the type of fish you plan on purchasing. There are three basic types of heaters available. There is the aquarium heater that simply hangs on the side of the tank. The hanging types of heaters are the most basic heating unit and are okay for use in smaller aquariums.
Everything relies upon the size and kind of your aquarium and the sort of fish you anticipate buying. There are three fundamental kinds of warmers accessible. There is the aquarium warmer that essentially holds tight the side of the tank.