Thermostatically controlled tank heaters, originally designed for aquariums, can also be used to maintain or increase the temperature of the nutrient solution. They are very easy to use: a dial is set to the desired temperature and the heater is put into the solution. It should be kept fully submerged at all times. When the nutrient solution drops below the set temperature, the tank heater will switch on and maintain the temperature.

Tank heaters have a small heated element housed within a glass tube, and although they run from electricity they are grounded and perfectly safe to use in water.