Reef safe is a distinction used in the saltwater aquarium hobby to indicate that a fish or invertebrate is safe to add to a reef aquarium. There is no fish that is completely reef safe. Every fish that is commonly listed as reef safe are species that usually do not readily consume small fish or invertebrates. Fish listed as reef safe also do not bother fellow fish unless in some cases, for instance tangs, they do not get along with conspecifics and sometimes fish with similar color or body shape. Every fish has a personality, is different, and, in some cases, are opportunistic feeders. Tangs, which by most accounts are reef safe, may in adulthood eat some crustaceans shortly after they molt. Many larger predatory fish, for instance eels and pufferfish, will adapt very well to a reef tank and will be problem-free as long as they have sizable tankmates and no crustaceans. Some aquarists have also had success in keeping smaller fish with predatory ones in reef tanks by adding the smaller fish at night, sometimes with newly rearranged rockwork.
Anemones (anemones, especially carpet anemones can eat fish and burn corals to death requiring specific placement for specimens in an aquarium)
Coral (there are aggressive types of coral which have sweeper tenticles that can burn other corals; these may require specific placement in an aquarium)
