You'll also need a Thermometer to make sure that your Thermostat heater is working correctly.
I have had instances where the Thermostat heater was not functioning correctly and the water got to cold and/ or to warm, resulting in the loss of some fish.
You get several different Thermometers for your aquarium.
I prefer using the ones that you can stick to the inside of the tank using the suction cup provided.
These are normally around R10.00 at your local pet store.