Quote Originally Posted by uafgrad View Post
I am using a 100W on a 20L and it brought the ambient temp of the tank up about 10F

If you are only worried about the cool end, then a 60 or 100W would probably do the trick just fine
Is the wattage to heat ratio the same as a bulb? If so I would think I need at least 100 watts, if the dimmer is o.k to use with the CHE (which I do not know yet) then I can simply turn it down if it is too much.