Dont buy a chiller ... use a heat exchenger

[mike31154]

While this might work well for you without a water meter & all the rain, it wouldn't be cost effective or environmentally friendly in areas where water is a bit more precious, like where I live. When things get too warm in the summer, I simply try to keep the room the fish tank is in cooler by running a portable air conditioner. Don't need a chiller since my lights are LED & don't add much heat to the tank.

As for your reasoning that it takes power, turbines etc. to produce electricity for a chiller, we are fortunate in BC to have mostly hydro electric power stations run by dams, not much coal burning or nuclear going on here. Still, it's never a good thing to waste power, you don't know what you got until you lose it. In any case, the water you're using to run your heat ex-changer is delivered to your house using some big honkin' pumps that the city runs using electric power.

Still, it's great that it works for you, but in my area, with the city cranking up the water rates & a meter in the basement, I think I'll keep running the air conditioner for the week or two during the summer when it's really hot.