Corals seem to adjust their feeding behavior as the majority expand their polyps at night to principally feed on zooplankton. Vertical migration might also be a way to avoid predation. It is also a way to escape from tactile benthic predators in the bottom of the reef, who are active at night. The number of emerging zooplankton is related to the structural heterogeneity and three-dimensionality of the reef. Branching corals generate more demersal plankton than plating corals as animals live within the interstices of the reef by day.
Some corals even show preferences for certain types of zooplankton.
The diet of the coral Millepora complanata mainly consists of copepods, while Alcyonium siderium shows a strong positive selectivity for ascidian larvae . Predation on their larvae by corals may even alleviate competition by decreasing the competitor's recruitment. Other meroplankton species would be larvae of crabs, lobsters or mussels. To support coral reefs with their enormously diverse and dense assemblages of organisms, input of nutrition from waters that overflow the reef is necessary. The open ocean is therefore a source of zooplankton that gets washed over the reef in currents and is stripped from the water by planktivorous fish and filter feeding organisms.