I run a 100 watt CHE and heat cable in my 50 gal tank (on a thermostat) and that works great with our Canadian winter and early spring. The temperatures here are all over the place so it is getting tricky but I watch the tanks carefully. Hopefully I will go PVC when I can get some $$'s ahead (have to sell some stuff - anybody want to but a guitar and amp - seems like snakes are taking up all of my practise time!)?