300W Glass Heater

50W heater = 20-50L Aquarium

100W heater = 50-100L Aquarium

200W Heater = 100-200L Aquarium

300W Heater = 200-300L Aquarium

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.