I was surprised to discover that heating a domestic aquarium can cost as much as $50 a year.
Plasma TVs give off enormous amounts of waste heat. So today’s invention is to create a fishtank with a plasma tv on one side (probably facing outwards, so you don’t have to watch your programmes through waving kelp). Much of he waste heat from the screen’s electronics can be used to heat the tank’s water.
This might be mounted on a vertical-axis turntable, so that one can choose the ‘fish channel’ by rotating the system.
Obviously you’d need remote speakers, so the poor fish weren’t disturbed by the sound.