A unique and refreshing simulation, El Fish lets you breed -- err-- fish and watch them live in a virtual aquarium. Every aesthetic factor involved in aquarium design is at your disposal, including tank decorations, types of water, etc. The program does not profess to create a realistic ecosystem: rather, it is aimed at simulating different types of fish you create (which are virtually unlimited, thanks to an ingenious and robust fish design interface). After you're done with designing, there's not a whole lot to do, but watching your creation on screen is quite relaxing :)