Why do tropical fish come in so many iridescent colors? The answer is different for each species. Spanish hogfish and other members of the Wrasse family use their stripes and brilliant hues to signal larger fish to come to be cleaned of parasites and dead tissue. In return the "cleaners" get a free meal. Multicolored bars, stripes, and splotches blur the outline of sergeant majors (Abudefduf saxatilis), foureye butterflyfish (Chaetodon capistratus), spotfin butterflyfish (Chaetodon capistratus), rock beauty, and spotlight parrotfish (Sparisoma viride) making them difficult for predators to see against the coral reef's complex background.
Some fish can change colors at night, to conceal themselves from nocturnal predators. The moray eel blends imperceptibly with the reefs, catching unwary fish with its vise-like jaws and needle-sharp teeth.