Our salf water fish tank already has a lot more life than we were aware of. We discovered clams, shells, and starfish, in additon to the two clownfish and two silverfish we already have. There is no distinct difference between the silver fish. I did notice, however, one of our clownfish has a spot by its tail. This fish also appears to be superier to the other because it is often times followed by the male. Maybe this is some sort of mating notion. Hopefully I will learn more about animal behavior and ethology with my upcoming project.