Heater must always be located in an area with strong circulation of water. If water movement is insufficient, the thermostat will not function accurately and desired temperature will not be obtained throughout aquarium. You should be able to observe that when heating (lamp on), the warm water is circulated away from heater before rising to the zone of the thermometer scale. Choice of correct watt is important. Use the table to find the correct watt depending on the size of your aquarimand the difference between room temperature and the desired aquarium temperature. It can be immersed upto the depth of 120cm 20C-32c Ac 220-240v 50/60hz Power 300w
