One of the most popular aquarium fish, fancy guppies are guppies that have been selectively bred to show vivid colors and marking; this is especially apparent in their flowing caudal fins. They are live-bearing, social fish and should not be kept alone. While you may see some occasional nipping behavior, guppies are generally peaceful fish. They will thrive on a diet of tropical fish flakes supplemented with brine shrimp, blood worms, and finely chopped high quality vegetables. They have a lifespan of up to about three years, but that doesn't mean yours will live with you for that long -- you very well may have picked out a guppy that is already 2 years old!