Because of the variability in growth habit that this coral exhibits, it has been the subject of much confusion as to its taxonomy, being described under a number of different names from different localities.

In 1898, Hickson decided that the variations in morphology were due to environmental factors and that Millepora alcicornis was the valid name for all these species.

Explaining this in 1941 Crossland wrote "I cannot resist the remark that the one thing quite certain about the many forms of Millepora is that none of them have any resemblance to an elk's horn, except perhaps that from the West Indies".

Later development is in the form of plates or blades in habitats with much water movement such as the surf-pounded outer edges of reefs.

In calmer waters, such as in deep lagoons or more sheltered parts of the reef, a more upright, leafy or branched structure develops which can grow to 50 centimetres (20 in) tall.

They are connected internally by a system of canals and are concealed behind pores in the skeleton, the surface of which is smooth and lacks the corallites of true stony corals.

Stings from the cnidocysts immobilize an item of prey and the tentacles thrust it through the mouth of an adjacent gastrozooid, from where it passes into the stomach for digestion.

These are photosynthetic organisms which provide their hosts with energy and in return benefit from a protective environment in a well lit position.

[7] A number of species of shrimp and fish take refuge among the branches of Millepora alcicornis, seemingly immune to the venom.

[7] It has been found that when Millepora alcicornis grows in close proximity to an arborescent gorgonian sea fan, the fire coral becomes aggressive.

It produces "attack" branches which grow out sideways towards the sea fan, develop into hand-like structures and encircle and smother it.

This aggressive action is specific to gorgonians and does not happen in response to the close presence of other live or dead corals, other sessile invertebrates or open water.

[4] The toxin has been investigated and is a water-soluble protein, 40 μg of which provides a median lethal dose to mice weighing 20 grams (0.71 oz).