As with any marine species, water quality plays an important role in ensuring they remain healthy. Being an invertebrate, shrimp do not tolerate anything less than reef grade water. If you can provide consistent water quality, you should have no trouble at all in being able to keep your pet healthy and free of problems.I prefer to keep my shrimp in their own dedicated tank for breeding purposes and observation. Therefore, I have put my shrimp breeding system in front of my reef aquarium's sump in order to facilitate water changes between the two tanks. As long as the reef aquarium has reef grade water quality this arrangement makes such a task very easy to accomplish and avoids any acclimation issues.
If you must use a synthetic salt mix, prepare the water at least two days in advance of it being needed to allow it to age and become properly mixed and aerated. Prior to use,ensure the new waters pH, salinity and temperature match the water the shrimp are in. They are easily affected by sudden changes and any water changes done with synthetic mixes should be gradual, doing no more than ten to twenty percent at a time, allowing a day between changes. When using my reef aquarium's water, I have changed seventy five percent of their water with no ill effects. Again, I must stress the importance of water quality and not shocking the shrimp with rapid synthetic water changes. These factors alone account for many shrimp deaths.
Being a timid species, it is also vital to ensure their aquarium is safe from predators or other animals that may harass them. Even a fast moving fish passing by can cause these shrimp stress and they may go into hiding and be unable to properly eat. For breeding purposes, I feel a tank dedicated to a single mated pair is a must. As pets, taking the simple precautions of having pump inlets protected and any possible predators removed will make keeping this species a simple matter. With good water quality, a peaceful environment and the proper food, you should have no trouble in maintaining this species for a good many years.
A Male (left) and Female (right) Mated Pair
This may not be easy for those that do not have access to a variety of starfish. While I have the luxury of being able to collect any starfish myself. For those of you that have to purchase starfish in order to feed these shrimp, you may wish to use some of the more prolific starfish such as the common Asterina species found commonly hitch hiking in on purchased live rock. Over the course of time, I have collected a variety of starfish species in order to determine which are found palatable or not, to the shrimp.If starfish are not available, in a pinch you can also try adding a small sea urchin. It has been reported that these shrimp have been known to eat the tube feet of sea urchins when starfish become scarce. I have tried small sea urchins, but my shrimp paid them no interest. I like to ensure that the shrimp have at least one decent meal each week, although they are capable of going three to four weeks without food. By keeping them well fed you will increase your chances of the female producing a great many more eggs.
In order to avoid having to feed an entire starfish at one time it is a common practice to cut off one of the starfishes arms and feed that to the shrimp while keeping the remainder of the starfish in another aquarium. In due time, the starfish will regenerate its lost arm. By keeping a number of starfish, you can rotate through the starfish, having them each donate an arm when required. I find this method of feeding to not only be less wasteful of starfish, it also allows the shrimp to feed right away. It can take a few days for the shrimp to actually break through a starfish in order to get at the internal parts that they eat.
Please do not add more than one starfish or starfish arm at each feeding. It is very common for the shrimp to combine their feeding efforts onto one starfish or starfish arm. Leaving the second starfish to crawl off, possibly wounded or having a second arm decay within the aquarium.
When feeding the shrimp break off and release a great many of the starfishes spicules. These are microscopic structures that give the starfish its bodily support. Such spicules resemble microscopic needles which, I am sure, would be an irritant to corals. To reduce any chance of coral irritation when keeping harlequin shrimp in a reef aquarium, I would suggest using a micron filter to try and reduce the number of free floating spicules. Or, better yet keep your shrimp in a dedicated tank of their own.
Once the feeding shrimp kill the starfish I do not allow it to remain in the aquarium longer than three to four days to avoid having the starfish pollute the aquarium water. Once a live starfish has been introduced to the aquarium, I take it out after two weeks whether or not the shrimp are done with it.
While being fed, I perform daily water changes and continue to do so for a few days after the starfish carcass has been removed. A week later, I will feed the shrimp again. This is done to ensure the shrimp have enough energy for breeding, spawning and molting. If the shrimp are being kept solely as pets, then I would feed them at least once every two to four weeks. The times I have noted as to how long a starfish will last and/or degrade are simply averages. It will vary based on the size and species of starfish and how the shrimp happen to dismember the starfish.
Acceptable Starfish species : Listed below are the starfish species that I have found to be a good food source for the harlequin shrimp. I have tried numerous brittle star species but the shrimp seem to be afraid of these and will not eat them. I believe this is because brittle starfish are fast moving and as they rapidly try to find a hiding place the shrimp are intimidated.
If you do decide to try other starfish than the Linkia species, keep in mind that many of these starfish are predators of corals and other invertebrates. Should they escape the clutches of the harlequin shrimp, they could pose a real threat to your other reef inhabitants. This is yet another good reason to keep these shrimp in a dedicated aquarium of their own.
When deciding upon a species of starfish to be used with the "sacrificial" arm method of feeding, I would chose the Protoreastors (Choc.Chip Stars) since they are easy to maintain and feed upon readily obtained seafood meats such as clams and oysters. Such a steady, meaty diet will ensure that the starfish can regrow its lost limb(s) much faster than other starfish groups. Species such as Linkias may not find their dietary needs being met and would most likely take a great deal longer to replace lost limbs, if they survive long term to begin with.
Protoreastor nodosus Fromia Imdica
Depending upon their health and quality of diet, the harlequin shrimp will molt an average of once each month. Prior to molting you can see the exoskeleton looking like an old dirty "skin". This seems to cause the shrimp great irritation just prior to molting. They will constantly pick at themselves as if trying to speed up the process by making the exoskeleton more loose by their tugging at it.As shrimp and other crustaceans grow, their exoskeleton does not grow with them and they must form a new exoskeleton to match their new size. During the period between molts they also repair themselves. If an antennae, leg or claw is lost new ones will grow and become evident after molting. It may take more than one molting period to fully repair any damaged or lost limbs. Keeping the shrimp well fed and in water of good quality will ensure they have the nutrient resources to complete such tasks. Even with such care, things can still go wrong for the shrimp during the repair process and the actual molting event. It is during molting that most shrimp losses occur.
I have noted that over the course of a few months, a new pair will synchronize their molting. My pairs seem to do their molting within the same day of each other. This could be coincidental but is most likely done to facilitate mating. I am not in the habit of dosing my shrimp's aquarium with iodine and have not observed any ill effects from not doing so. I feel that the belief that shrimp somehow need iodine in the water in order to properly molt is unfounded. Keeping the water at the same calcium and alkalinity levels as you would for a coral reef aquarium should provide for the needs of the shrimp.
Once molting has been completed, do not be surprised if the shrimp disappear out of sight for an extended period of time. They are extremely vulnerable (soft) to predators and they know it. After a few hours, their new exoskeleton will harden and they should make a reappearance. If not, you may try enticing them out with a starfish.
Looking a bit haggard just prior to molting
This only occurs directly after the female has broadcast her spawn. Once all of the larvae have hatched, it is normal for her to molt the next day. Once she has molted she is immediately ready to form a new clutch of eggs, but first needs the male's contribution as the eggs are fertilized as they pass by the deposited spermatophores. The male will lift the female's tail and turn himself onto his back and join with the female. It is at this time that the male applies spermatophores or sperm sacs close to the opening of the female's genital duct. The sperm sacs are shed from a pair of holes at the base of the last legs and the eggs from holes on the third legs.Within 24 hours of mating, the female spawns, releasing eggs which become fertilized as they pass by the spermatophores. The female holds the fertilized eggs in a brood chamber under the abdomen "glued" onto hairs of the pleopods. The eggs remain attached to the female during incubation. When mating is completed, the male will "piggy back" on the female to guard her against the advances of other males. He will continue to be protective of her in this manner until she forms a new clutch of eggs. Once the new clutch is formed the female will reject the advances of all males, including her mate.
The male guarding the female Male lifting the female to gain access The actual mating event
When compared to other shrimp species, the harlequin shrimp seems to come with some extra parts, or parts that are not easily identified as to what they are due to their flamboyant structuring. Trying to find, let alone determine, what the various head and claw structures are can be a bit of a challenge as the shrimp tends to shield itself, making its smaller details difficult to see. 
The eyes appear to be well developed and allow the shrimp to make out details, if the object is close enough. From a distance, they most likely can only make out movement and the differences between light and dark objects. 
The mouth is not readily visible since their food particles are extremely small, hence no need for a large opening. The mouth can be seen as the vertical slit shown in the photo.
The Maxillipeds are appendages modified to function as mouth parts in some shrimp species. I have not seen the Harlequin shrimp use them as such. In this species they may serve more as a means to recognize friend from foe as mated pairs often touch with their maxillae as if taste testing each other.The Pereiopods : All shrimp have five pairs of Pereiopods ( legs ), most of which serve specialized or multiple purposes. Usually only the last three pairs are used for walking, while the first two pairs are modified to serve as claws for gathering food and as weaponry.
Details of first pereiopods, which rules out their use to inject vemon as some believe is possible
The second Pereiopods, which are armed with a claw (chela) are referred to as Chelipeds. The claws of the harlequin shrimp do not appear to serve any purpose other than as offensive and defensive weapons. They are used offensively to "pinch" an opponent or defensively as a shield when under attack or feeling threatened. I have also noticed that when feeding, the shrimp will use its large claws as a shield to hide its feeding activity. This is most likely done to prevent drawing attention to the movements of feeding and to protect its vulnerable mouth parts.
The third, fourth and fifth pairs of Pereiopods are primarily used for walking. The pereiopods also bear the sexual organs, which are the third pereiopod in the females and the fifth pereiopod in the males.
FAQ - " Can I keep more than one pair in an aquarium? " This would of course depend upon the size of the aquarium. Being that these shrimp are very territorial and defend their mates, I would only attempt a second pair in very large aquariums. Even then, there is no guarantee that one pair or the other will not seek out and attack their rivals. The males may also attempt to move in on the other males female. I would not risk it myself.
" Can I keep other species of shrimp with the Harlequins? " Again, in larger aquariums that give each species its own territory, I see no problem in keeping other commonly kept species of decorative shrimp in with the harlequins. If there is a squabble over territory, or if threatened, the harlequins are quite capable of warding off any would be aggressor. This of course does not mean that species such as the mantis and some pistol shrimp species are acceptable.
" Is there an acceptable food alternative for harlequin shrimp? " No, not that I am aware of. Starfish are their only food source. This factor alone should be a large consideration when deciding if you are going to keep this species of shrimp or not. Some would argue, and with good cause, that the keeping of harlequin shrimp places an unnecessary strain on wild starfish populations. This is a moral decision that I will leave up to you.
" Do harlequin shrimp inject the starfish with a toxin to make it stay still while feeding? " No, there are no shrimp capable of envenomation. What happens is that as the starfish falls under the grasp of the shrimp it simply withdraws and remains still while under attack. As long as the shrimp remains on the starfish and constantly picks at it, the starfish will feel constantly under attack and remain withdrawn, unwilling to move. Should the shrimp move off of the starfish and the starfish has not been gravely wounded it will try to slowly crawl away. Should the starfish die and start to decay, the shrimp will move off of the starfish. This should be your clue to remove the corpse. I also believe that this is the one reason that harlequin shrimp do not attempt to capture and eat the fast moving brittle starfish, simply because brittle starfish do not withdraw and remain still. They put up a fight of sorts and do not ever give up in trying to get away. This along with their quick actions makes it impossible for the shrimp to keep the brittle starfish under control. If harlequin shrimp were capable of toxin use, then the brittle starfish would be just as vulnerable and readily eaten as are other starfish species.
Selling $40 a pair
