|Adding new fish to an established reef aquarium can quickly cause disaster. You must allow the new fish time to adjust to its new home without constant harassment from established tank mates. To best achieve this:
Quarantine the "bully": Whenever possible, remove the established "bully" fish from the aquarium and house it in a separate quarantine aquarium. Or, keep it in a holding container located within the main aquarium. Breeder chambers and in-tank refugiums make ideal holding containers for small and moderate sized fish. Keep the "bully" in isolation until the new fish becomes comfortable in its new home, and is eating well.
Divide the aquarium: Catching a fish within a reef aquarium for removal is often very difficult if not impossible so your only option may be to separate the bully and newcomer with an aquarium divider. Lighting egg crate, available at any hardware store, offers an easy and economical solution to dividing your aquarium. Simply choose a dividing location in the aquarium (making sure to provide the new fish with hiding places), and cut the egg crate to fit the location. Secure the divider in place with plastic zip ties and suction cups (also available at hardware stores). Add your new fish and remove the divider when the fish become accustomed to each other typically within a few days. Please note: Do not use tank dividers made with metal, as metal corrodes very quickly in saltwater and leaches harmful elements into your aquarium water.