With utility prices constantly rising and a world finally trying to become more "Green", I'm wondering what ways people have designed their systems to be more efficient. Anyone out there using geothermal energy to heat or cool tanks, or does anyone have more information how a heat exchange system for your tank might work? What kind of equipment would be needed? I know natural light is occaisonally used to suppliment tank lighting, has anyone taken this a step further and used solar energy in any other ways? There are alot of solar powered water pumps available, they dont seem to have made their way into the hobby yet though. Reccommendations on high efficiency lighting, reflectors, pumps, powerheads, and anything else applicable would be greatly appreciated. Im not currently planning a system change, I just think this could be a very useful topic for a hobby that is already taking so much from nature, not to mention from our wallets.