Anemone shrimp have adapted to live among the stinging tentacles of sea anemones. Both the anemone and the shrimp benefit from this relationship -- the sea anemone protects the shrimp and the shrimp eats parasites and brings extra food to the anemone. Four genera of anemone shrimp exist.
Of this genus, Alpheus armatus shows up most often in aquariums. This species goes by the names pistol shrimp and snapping shrimp. It can click its claws loud and strong enough to stun fish. It uses this ability to protect its anemone from the few organisms that can get past the anemone's sting. A male-female pair can share a tank, but more than a pair will fight until you are left with a single pair. These shrimp will also eat certain predatory aquarium pests, like fireworms.
Anemone shrimp from the genus Lysmata also sell under the name cleaner shrimp. In addition to living with sea anemones, these shrimps set up "cleaner stations" on coral reefs. At these stations, fish swim up to allow the shrimp to eat their parasites. Cleaner shrimp have a similar relationship with sea anemones, eating parasites in exchange for a safe home.
The Periclimenes anemone shrimp are more gregarious than most anemone shrimp. They can live in large groups within their host anemones. There are at least 10 specific species. Many species of anemone shrimp in this genus have clear bodies. This helps them blend in with the tentacles of their host anemone. In the wild the majority of some species of sea anemones host these shrimp.
The anemone shrimp from the genus Thor have a curious common name: sexy anemone shrimp. These shrimp can sway the rear half of their bodies to mimic the undulations of the anemone's tentacles. At some point, someone thought this motion resembled a seductive dance, and the shrimp got their common name. At least two species of anemone shrimp come from this genus. In aquariums, sexy anemone shrimp tend to hang out perched on coral instead of living in anemones.