The heater is a Visi-therm 300watt model.

This sits in the sump in an area of good water flow & the temperature is set at just under 27C. This is enough to keep the tank stable at night when the temps could go below 24C without a heater.

In the daytime, heat from the Halides take the temp up to 27C which is when my Eco-cooler kicks in.