Spectrum Brands Pet introduced GloFish Sharks to its popular line of GloFish fluorescent fish. They are members of the minnow family, not actual sharks. Since these fish can reach up to four inches in length, they should only be placed in aquariums 20 gallons or larger. They also serve as bottom feeders, giving the added benefit of cleaning up leftover food, unsightly algae and small nuisance snails. Two colors are available: Sunburst Orange and Galactic Purple.