The brook stickleback is the most common stickleback species. It's a tiny, hardy fish that can live almost anywhere. Weedy little creeks, of course, are its favorite home. This fish is very aggressive and is incompatible with most other fish species for the purposes of housing them. In the aquarium, they have a nasty habit of biting the eyes out of other fish. With an extremely tiny mouth, brook sticklebacks can consume only the smallest organisms.