Fig. 4. (A) Fishes (Chromis viridis) sheltering in the hypoxic water inside a coral colony (Acropora sp.) on the Lizard Island reef at night during low tide. Oxygen levels between the coral branches varied between 12 and 20% of air saturation. (B) A predatory rockcod (Epinephelus spilotoceps) lies outside the coral and provides a good reason for the smaller fishes to use the coral as nocturnal shelter. Photo G. E. Nilsson.