Why bore your fish with a humdrum aquarium when you can house them in the Spillarium, a spherical 19-litre tank that features colour-changing LED lights and a spilling waterfall that plunges into a bigger fish's ceramic maw.
Though the MythBusters proved that goldfish don't reallyhave a three-second memory - they trained fish to swim through mazes and found that their times increased as they became familiar with the course - the Spillarium fish tank will constantly make your fish swim like its life depends on it. Lest that little fishy fall into a bigger fishy's mouth, carried to his cannibalistic fate by a stream of water that continually spills out of a hole in the tank.
The waterfall effect is designed to circulate water in the aquarium; the water is purified in the base and recycled back up into the sphere. But I like to think it's for keeping your fish on their best behaviour. [Oh Gizmo]