porcelain crabs are perfect companions for fish and inverts:
The Porcelain Crab is common throughout the tropical oceans of the world, and has a flat, round body with two large front claws. They are brown and orange in coloration with bright blue spots. These crabs have a pair of front arms called maxillipeds, which have ends that are feather-like in appearance. They use these appendages to filter the water for any passing food. They are peaceful and interesting invertebrates for the marine aquarium.
Porcelain Crabs live together in pairs typically found within or under rocks in nature. The ideal aquarium will contain plenty of live rock for both hiding and feeding, and will not contain any fish or invertebrates that may bring harm to these peaceful invertebrates. They are reef safe, and will not harm other invertebrates or corals.
The Porcelain Crab constantly filters the water for planktonic food, but will also scavenge for larger meaty portions. Offer the crab small bits of fish, shrimp or meaty food, as well as foods designed for filter feeders.