Visi-Therm Aquarium Heaters Visi-Therm automatic aquarium heater has a unique direct-reading temperature setting feature, which eliminates guess work and makes presetting temperatures very simple.

The desired temperature is indicated on an easy-to-read thermometer-type scale and is accurately maintained by the precision thermostat. Visi-Therm is completely waterproof and totally submersible. All these features make it the choice of experienced aquarium hobbyists.

As a guide 100 watts will heat 100 litres so 300 watts will heat 300 litres and so on...