Show me a filter that requires 500 watts please, for a normal sized tank.
Like I said above though, it's on the same order of magnitude of making toast in the morning, or keeping your beer in a fridge. Add up all the energy being consumed in the world keeping beer cold (never mind the power consumed baking the bread, or brewing the beer) and it will outweigh the power consumption on aquarium hobbyist filters 10x or more. You gonna stop eating toast or using a fridge because of that?
I know it's a bit of a side rant, but this whole "power smart" "fuel economy" craze pisses me off. Not many people really and truly understand how insignificant the contribution of even an old, smoky 6+ liter V8, or a large air conditioner reaally is. Anyone know how much energy it takes to launch a large airliner? more fuel than most cars use in a year. Or the cost of energy to manufacture the glass you love to look at your fish through? How about the giant cost of energy to manufacture "environmentally friendly" cars? google "dust to dust" an environmental friendliness study done on modern vehicles. A Hummer is more environmentally friendly than a Prius. Anyways... there are better things you can do for the environment than getting rid of your auxiliary fish tank filter. If you want to really save the environment, start thinking about how much energy you use indirectly by buying things that require enormous energy investments to make.