Thought this list might be useful. Post a fish or critter that might be considered reef safe, especially if you have specific experience with the animal in question. Do list why you consider the animal a threat to a reef setup. For example, no need to list clown triggers or parrot fish, but some of the larger angels can work under some circumstances. This is for the borderline cases. Camel shrimp--target polyps and zoanthids. Leave sponges and other motile inverts alone. Engineer goby--digs tunnels under rock work and can easily topple live rock and corals. Tends to bury sessile invertebrates that are on the sand bed or lower portions of the tank. If live rock is on a stable platform, can be accomodated. Large hermit crabs--tend to knock over corals and rocks, can kill a fish that's ailing. Octopus--safe with sessile inverts, but primary predator on motile inverts and small fish.