Common name: flat rock crab

General information

The Flat Rock Crab, Percnon planissimum, is a species of crab that is often overlooked in the reefkeeping hobby but can be a beneficial addition to a marine aquarium. It is a close relative of the more commonly known Sally Lightfoot Crab (Percnon gibbesi), hence sometimes referred to as Sally Lightfoot's Younger Sibling. This crab is known for its flattened body and swift movements across the rocks and substrate.

Care

Flat Rock Crabs are relatively easy to care for. They require a tank with plenty of live rock and a sandy substrate to mimic their natural environment. They are scavengers by nature and will feed on various types of detritus, leftover food, and algae, helping to keep the tank clean. However, they should be monitored to ensure they are not preying on small, slow-moving fish or desirable invertebrates.

Reproduction

In the wild, Percnon planissimum engages in a complex mating ritual that involves courtship displays and the male protecting the female during the molting process, which is when she is most vulnerable. In captivity, breeding is less common, but with a well-established environment and careful attention to water quality, it is possible.

Habitat

The Flat Rock Crab is found in the Indo-Pacific region, from the Red Sea to the western Pacific. They inhabit shallow reefs and rocky outcrops, often seen scuttling quickly over the surface in search of food or shelter. They are adept at hiding in crevices and under rocks when threatened.