GloFish are relatively hardy, easy to keep, and get along well with other fish. However, not all fish are this way, so if you have other fish in your tank or are adding new fish to your GloFish tank, be careful to choose fish that can all live together in a similar environment. Here are a few key points that may be helpful: (1) Like their non-fluorescent counterparts, GloFish are schooling fish and should ideally be kept in groups. This is particularly important with GloFish Barbs (Electric Green® and Starfire Red®), which can potentially become aggressive if they are not kept in groups of five or more. (2) Be sure not to crowd too many fish into a tank. (3) Please avoid keeping fish (even just one fish) in a small bowl. Recommended stocking densities vary depending upon the literature source, tank configuration, filtration system, and other factors, so making a specific recommendation is difficult. We recommend consulting with the experts at your local fish store before starting a new aquarium or adding to an existing community.