If you're looking for a cool idea for a fish tank and you happen to be an Apple fan, then the MacAquarium is the one for you. It's made from an iMac G3 and you'll probably get only about 3 gallons worth of space in it so it's a great idea for a nano-tank.
If you're interested, you can buy a MacAquarium for $250 or you can buy the kits to make your own for $175 (although it'll take some know-how and safety measure to properly take apart the iMac).
To learn more about it...click here!.
and IF you do get one, make sure to let me know! I want to see it in action!