Crown-of-thorns starfish substrates with their arms and, when offered a choice of substrates, tend to settle on coralline algae, which they will subsequently feed on. In the classic pattern for echinoderms, the bilaterally symmetrical larva is replaced by a pentamerously symmetrical stage at metamorphosis, with the latter's body axis bearing no relationship to that of the larva. Thus the newly metamorphosed starfish are five-armed and are 0.4–1 mm diameter. (Note the size of the tube feet relative to the size of the animal.) They feed on the thin coating layers of hard encrusting algae (coralline algae) on the undersides of dead coral
Crown-of-thorns starfish hypotheses focused on changes in the survival of juvenile and adult starfish - the "predator removal hypothesis": Many of the reports of fish preying on "Acanthaster" are single observations or presumed predation from the nature of the fish. For example, the humphead wrasse may prey on the starfish amongst its more usual diet. Individual puffer fish and trigger-fish have been observed to feed crown-of-thorns starfish in the Red Sea, but there is no evidence that they are a significant factor in population control. A study, however, based on the stomach contents of large carnivorous fish that are potential predators of