In a similar way to Clown Fish, Anemone shrimp utilise sea anemones as a place of refuge.
Tropical anemone shrimp include members of the genera: Alpheus, Lysmata, Periclimenes and Thor. Most anemone shrimp are totally dependent on sea anemones and are rarely found without them in the wild, however, that is not to say that they don’t roam around on the substrate near their host, but they are always nearby. Their small size and lack of defence structures mean they are vulnerable outside of their anemone host. At night, when many anemones close up, their shrimp associates may retreat into holes near the anemone’s base.
Some shrimp have specific preferences when it comes to an anemone host, while others are a bit more less picky. Examples of some Atlantic species with “partner preferences” include: the anemone shrimp (P. rathbunae) and sun anemone (Stoichactis helianthus), the spotted cleaner shrimp (Periclimenes yucatanicus) and the giant anemone (Condylactis gigantean), and Pederson’s cleaner shrimp (P. pedersoni) and the corkscrew anemone (Bartholomea annulata). While they may have favourites, some of these species can be found in more than one anemone host species. One of the least selective shrimp is the sexy shrimp (Thor amboinensis) — this species can regularly be found with a number of different hosts, including tube anemones (cerianthid) and feather stars.
Food and Feeding Behaviour
Anemone shrimp feed on tiny organisms and detritus that stick to the host’s mucus; they may also eat the slime itself. There are also many anemone shrimp that eat parasites from passing fish. Fish will visit the anemone and pose for servicing. The shrimp will jump onto the stationary fish and inspect them for and remove certain parasitic pests. Anemone shrimp known to clean include the saddled shrimp (Periclimenes holthuisi), magnificent shrimp (P. magnificus) and Pederson’s cleaner shrimp (P. pedersoni). While the sexy shrimp (Thor amboinensis) does not clean fish, it has been observed grooming large mantis shrimp.
Some anemone shrimp also eat their host. This is the case with the clown anemone shrimp (P. brevicarpalis), which can negatively impact the host sea anemone due to tentacle feeding. Other Periclimenes species (e.g., the ornate anemone shrimp, P. ornatus) are also known to feed on the tentacles of their hosts. The sexy shrimp, too, has been indicted as a tentacle-eater, especially when underfed in captivity. According to some hobbyists, it may also eat zoanthids.
As mentioned, some anemone shrimp will eat their host (e.g., clown anemone shrimp, P. brevicarpalis). This is especially true if the shrimp is not getting supplemental feeding from the aquarist. While these shrimp are likely to collect food that you introduce for your fish, you may want to target-feed your anemone shrimp by directing a stream of food at your shrimp’s host by using a pipette or turkey baster. Any meaty food should do, for example, bits of frozen mysid or finely minced seafood (take frozen shrimp or fish and use a cheese grater to produce appropriately sized morsels).
Acclimating to a Sea Anemone
Anemone shrimp have to acclimate to their hosts. When a “non-acclimated” shrimp contacts an anemone, the anemone’s tentacles (as a result of the stinging nematocysts) will adhere to the shrimp, causing the shrimp to rapidly jump backward and attempt to tear itself away from the anemone. An acclimating shrimp will endure the occasional sting and will gingerly make contact with the anemone’s tentacles and pick at the integument of its potential host. Once it has fully acclimated, which normally takes one to five hours, the shrimp will move about the anemone unimpeded, and the host will not respond at all to the presence of the shrimp.
You should never force an anemone shrimp to enter a sea anemone. If you do, the shrimp may be stung and may, on rare occasions, be eaten. After acclimating the shrimp to your aquarium (preferably by dripping water into the bag it was brought home in for an hour or two), release it near its potential host, and let the process occur on its own time. Of course, this can be problematic if you are counting on the anemone to provide refuge from potentially dangerous fish tank mates. If you want to keep an anemone shrimp and host with possible predators, add the shrimp to the tank first.
Anemone shrimp may vary in their social behaviour. For example, the snapping shrimp (Alpheus armatus) is highly territorial. However, most other anemone shrimp are not territorial. P. rathbunae is usually found singly or in pairs. Other species of Periclimenes are regularly found in groups (e.g., dozens of P. holthuisi can be observed on larger anemones), while assemblages of sexy shrimp (T. amboinensis), which can number more than 20 individuals, may also share a host. These group-forming species tend to be peaceful toward one another. These groups can consist of both males and females or occasionally consist of a single sex. For those anemone shrimp that clean, the size of the group is often dependent upon how many fish visit the anemone. If the anemone is in an area frequented by fish to clean, more shrimp will occupy the host.
At least one species, Pederson’s cleaner shrimp (P. pedersoni), has been observed to chase conspecifics away from a specific area of their host (usually the center of the oral disc). It turns out that this area tends to attract the most potential fish clients for cleaning. In this species, pecking orders have been observed, where larger individuals have more ready access to the best sites on the host and first access to fish that come to be cleaned.
Keeping Anemone Shrimp
Most anemone shrimp will not do well in your tank unless you keep them with an appropriate host. Not keeping anemone shrimp with an anemone will result in the shrimp hiding incessantly and is more likely to be picked off by a fish tank mate.
A nano reef is often the best home for an anemone and anemone shrimp. Of course, as with a larger tank, you will need to make sure you have enough light and water movement to keep an anemone healthy. You will also want to select the anemone you keep in such a tank very carefully, steering toward smaller, more hardy species. Some anemones that would work best for the nano tank include Condylactis gigantean, the colonial form of Entacmaea quadricolor, Lebrunia danae and some of the Phymanthus species.
Many anemone shrimp can be kept in groups. In fact, many species, such as the saddled cleaner and sexy shrimp, will do best if kept in groups of three or more. Some anemone shrimp that naturally occur singly or in pairs include the clown anemone shrimp (P. brevicarpalis), spotted cleaner shrimp (P. yucatanicus) and red snapping shrimp (Alpheus armatus). More than one of these shrimp can be kept in the same tank, but attempt to get a heterosexual pair or provide more than one appropriate host. In some species (e.g., sexy shrimp, clown anemone shrimp), females are significantly larger than males, while in others (e.g., Pederson’s cleaner shrimp) the males are larger. Hermaphroditism has been discovered in some anemone shrimp; for example, the sexy shrimp is a protandric hermaphrodite (females result from male sex change).
Unfortunately, because of their diminutive size, anemone shrimp are vulnerable to a wide array of fish tank mates. Even fish species that rarely bother ornamental crustaceans (fairy wrasses, Cirrhilabrus spp.) will pick off an anemone shrimp that strays too far from its host.
Here are some fish to avoid housing together with ornamental shrimp: Morays, Lizardfishes, Scorpionfishes, Frogfishes, Squirrelfishes, all groupers (including smaller sea basses), most wrasses, Sand perches, Triggerfishes, Tilefishes, Puffers, Porcupinefishes