If you keep tropical fish you will need a tank heater, this is to ensure the warm temperature stays within the temperature range for your fish. Remember to choose fish which will thrive in the same temperature and pH range, to ensure your fish will all be happy. This will reduce the risk of stress, illness and disease.
You also need to choose the right sized heater for your tank to ensure that it is strong enough to maintain a constant temperature. If your heater is not big enough, the water will take too long to reach the desired temperatures, if it is too big then it will heat up too quickly.
Always situate heaters next to the filter, so that the outlet stream of the filter circulates the heat around the tank more quickly.
Click image for more info.
