Sponge Decorator Crab

Decorator crabs are among some of the most interesting and unique species of crustaceans, known for their unique appearances. As their name suggests, decorator crabs are most commonly known for their habit of decorating their bodies with a variety of different things ranging from algae to sponges to even living corals! In their natural habitats, these animals use these living 'decorations' as a form of camouflage and protection from potential predators. Due to this tendency to collect items, it should be noted that decorator crabs may decide to wear any variety of things available to them in the home aquarium, including polyps that are not securely fixed to another surface (e.g. zoanthids and other soft polyps).

***When molting, most decorator crabs will meticulously move decorations from their old carapace onto the new one. For this reason, the immediate removal of molts is NOT recommended.

Quick Care Guide

Care Level: Moderate
Minimum Tank Size: 30 gallons
Temperament: Semi-Aggressive (opportunistic)
Diet: Omnivorous Scavenger
Reef Safe: With caution
Adult Size: Typically 1–3 inches across
Family: Dromiidae (sponge crabs)

How Sponge Crabs Decorate

Sponge crabs carry a living cap of sponge or sea squirt over their backs, held in place by their shortened, hooked rear legs. Over time the sponge can grow to fit the crab, forming a snug shelter that hides it from predators.

If the crab loses its sponge, or outgrows it after a molt, it will search for a replacement. Leaving a small piece of live sponge in the aquarium gives it a ready option.

Tank Requirements

Provide an established aquarium with plenty of rockwork and shaded ledges. Sponge crabs are mostly nocturnal and spend daylight hours tucked into crevices, emerging at night to forage.

Diet and Feeding

This crab is an opportunistic omnivore that scavenges leftover meaty foods, detritus, and algae. Offer small pieces of mysis, chopped seafood, or sinking pellets two to three times per week, ideally just after lights-out when it becomes active.

Temperament and Tankmates

Sponge decorator crabs generally ignore larger fish, but they may prey on small snails, ornamental shrimp, or sleeping fish when food is scarce. Keep them with medium to large peaceful fish, and avoid triggerfish, puffers, hawkfish, and large wrasses.

Reef Compatibility

Consider this crab reef safe with caution. Unsecured zoanthids, soft polyps, and small sponges may be picked at or carried off as decorations, so glue down frags and monitor the crab once it settles in.

Water Parameters

Temperature: 75–80°F
Specific Gravity: 1.024–1.026
pH: 8.1–8.4
Alkalinity: 8–12 dKH

Keep parameters stable and acclimate slowly to support healthy molting. Invertebrates are highly sensitive to copper, and copper-treated water or medications should never be added to an aquarium that houses them.

Common Considerations

• Leave molts in place: The crab may transfer its sponge from the old shell to the new one.

• Secure loose frags: Unattached polyps can be picked up as decorations.

• Mostly seen at night: A red or moonlight view is the best way to watch it forage.

• Offer a spare sponge: A small live sponge gives the crab a replacement cap if it needs one.