Suzy,
I have thought about the energy use also and my solutions were to
take down a couple tanks and give them away. I also have decided to
only use my heater when my tank temperature starts to drop below a
comfortable level for my fish; this usually occurs from November to
February (I live in the southern US). I have a 90 gallon tank and have
one biowheel filter and a powerhead running (with the air tube
connected). I also have an air pump running in the tank. Between
these things I think that I am getting enough aerobic treatement in my
tank. Good luck on that glass project. My tank has slate attached to
the back of it, I figure this insulates it a little bit.

James