But with the proper light, enthusiastic night dive buddies, and some knowledge of what's going on out there, you can really see some amazing fish behavior and nocturnal critters. The main difference between daytime and nocturnal migrations of schooling fish is their destination. Fish that feed during the day follow pathways over the reef or near the edge, never risking open water. Small plankton-feeding fish such as blue chromis usually stay within easy reach of coral, although they feed in the water column. Nighttime migrations are made up of fish that move out and away from the reef's protection, either to feed in the sand or grass flats or on plankton in the darkness of the open water.
Some schools break up into small groups and forage a short distance from the reef.
Others move as far away as a mile or so. Predators are not as great a threat to these exposed reef fish at night, although some of the smaller bottom-feeding fish sometimes fall prey to a lurking nocturnal scorpionfish or stingray. The majority of night fish are carnivores, out for a meal. Even the plankton changes. Small shrimps and crabs that live in the sandy bottom during the day migrate upward at night to feed on plankton, becoming fair game for the night fish.