Octocorals of the genus Heliopora are known to be abundant and to be capable of building large mono-specific stands on Indo-Pacific coral reefs. They have a calcium carbonate skeleton and although they are zooxanthellate, they have been observed to resist threats that have a negative impact on other reef-building corals, such as long periods of elevated seawater temperatures, and population outbreaks of predators, such as corallivorous Acanthaster crown-of-thorns sea stars. On the other hand, Heliopora corals can be harmed by aggressive competitors for space, but how they attack Heliopora is not well documented. Here, we illustrate examples from Indonesia in which Heliopora corals are overgrown and overtopped by corals of Porites rus and the genus Montipora. The nature of these interactions is discussed, and a hypothetical future scenario is presented in which Heliopora may become a more successful competitor and a more common reef coral species than it is today.
