Aquarium Heater Parts – Suction Cups, Magnetic Holders & More. Aquarium heaters are essential components to most fish tank setups. Maintaining a specific temperature is essential for the health and activity of many types of fish, particularly for the most popular tropical species. Pond Heaters help by warming the water and keeping the entire pond above freezing. This can be a costly feat however it is not essential to bring tropical temps just somewhere in the 40 degree range is plenty. These usually use a user programmable thermostat and work just like the heater in your home.