Harlequin Shrimp (Hymenocera picta)

Harlequin Shrimp at a glance

The Harlequin Shrimp (Hymenocera picta) is a small, boldly spotted reef shrimp from the tropical Indian and Pacific Oceans, and one of the most specialised animals a marine keeper can take on. It reaches about 5 cm, lives in pairs on coral reefs in the wild, and has a single food: starfish. Every other decision about keeping it, from the aquarium you set up to the companions it can share with, follows from that diet.

That makes the first question before ordering a practical one rather than a matter of tank size. Pellets, flakes and the mixed frozen foods that suit most marine crustaceans are not what this shrimp eats, so you need a dependable, continuing supply of starfish for as long as you keep it, alongside a mature, stable saltwater aquarium with plenty of rock to shelter in. With both in place it is a remarkable animal to watch at close quarters. If the food supply is uncertain, a more adaptable reef shrimp will be the kinder choice for you and for the animal.

The appeal is easy to see. Its appearance is striking, a body covered in large rounded spots whose shade and edging differ between the central Pacific and Indian Ocean forms. It is also a genuine specialist, an animal whose whole way of life is built around one kind of prey. Neither quality makes up for an uncertain food supply, so settle that question before anything else.

Before you order

• You have a reliable, continuing source of starfish to feed it, not just a first meal.
• Your saltwater aquarium is mature, with ammonia and nitrite at zero and steady readings.
• There are no starfish in the tank that you want to keep.
• Your fish are reef-safe, with nothing likely to prey on a small crustacean.
• The aquarium has live or artificial rock where the shrimp can hide while it moults.
• Someone can be at home to receive the parcel on delivery day.

Names and what you receive

You will often see this shrimp sold as Hymenocera elegans. The World Register of Marine Species treats that name as a junior synonym and gives Hymenocera picta Dana, 1852, a member of the shrimp family Palaemonidae, as the accepted name, which is why it heads this listing. Some authors still divide the genus in two: H. picta from the central and east Pacific, with deep pinkish-purple spots edged in yellow, and H. elegans from the Indian Ocean and west Pacific, with browner spots edged in blue. Whichever name you meet, the needs described here are the same: starfish to eat, stable saltwater and carefully chosen companions. When you read up on care, search under both names, because both are still in use.

Each purchase supplies one live Harlequin Shrimp. We don't quote a dispatch length for it, so treat about 5 cm as the size it can grow to rather than the size that arrives. Sex is guaranteed only when the selected option explicitly states male or female. This Hymenocera elegans listing has no sex-guaranteed option.

Gallery images have been digitally enhanced to improve image quality. Natural colour, pattern, size and maturity can vary between live animals. Some of the pictures show the shrimp against plants and driftwood; in reality this is a fully marine animal that needs a saltwater reef aquarium, never a planted freshwater tank.

If you are weighing it up against other reef shrimps, crabs and invertebrates, our marine invertebrates collection brings them together in one place.

Feeding a starfish specialist

Most marine crustaceans are easy to feed. OATA's care sheet describes the majority as omnivores that take algae, detritus and small meaty items, and suggests a varied menu of nori, small frozen foods such as brine shrimp, and pellets. The Harlequin Shrimp is the exception to that rule: Hymenocera picta feeds exclusively on starfish, and planning its food is the most important part of keeping one.

What it eats on the reef

Wild harlequin shrimps seem to prefer smaller, more sedentary starfish. Those are generally too scarce to meet their needs, so the shrimps commonly attack the crown-of-thorns starfish, a coral-eating species. An attack reduces the starfish's coral consumption while it is under way and kills it within a few days.

That is wild natural history rather than an aquarium feeding routine, but it tells you two things that matter at home: the shrimp eats living starfish, and it can work on one prey animal over a few days rather than finishing it in a single sitting.

Planning a supply before it arrives

• Secure the food first. Arrange where your starfish will come from before you order, and think about how you will keep that supply going for the rest of the shrimp's life rather than just its first weeks.
• Treat every starfish as food. Any sea star already in the aquarium, including an ornamental one you are fond of, should be regarded as the shrimp's next meal.
• Don't count on prepared foods. Pellets, flakes and frozen crustacean mixes are no substitute for starfish in this shrimp's diet.
• Size the supply to every shrimp. A second shrimp means more starfish, so plan for all the mouths in the tank.
• Brief anyone who helps. If a friend looks after the aquarium while you are away, make sure they understand that this animal cannot be kept going on the flakes or frozen food the fish receive.

Keeping the tank clean around feeding

A starfish that is being eaten slowly is still food sitting in the aquarium, and OATA's warning about overfeeding applies: a build-up of uneaten food breaks down and releases toxic waste into the water. Look at the remains regularly and lift out anything the shrimp has clearly finished with. Keep testing for ammonia and nitrite in the days after a new starfish goes in, particularly in a smaller system where waste has less water to dilute into.

Signs that feeding is going well

A shrimp that is eating well stays active, keeps its normal colour and moults as it grows. OATA lists reduced intake or lack of interest in food among the early warning signs in marine crustaceans, so watch whether your shrimp is actually working on the starfish you provide, not simply whether food is present in the tank.

If a starfish supply isn't realistic

Deciding that this shrimp isn't right for your aquarium is the responsible choice when its food can't be relied on. Many other marine crustaceans take the varied omnivore menu described above, and several have a useful role of their own. OATA notes, for example, that cleaner shrimps (Lysmata amboinensis) may eat parasites on larger fish, while peppermint shrimps (Lysmata wurdemanni) consume unwanted Aiptasia anemones.

Setting up the aquarium

This is a marine animal from warm coral reefs, and it needs a properly filtered saltwater aquarium. OATA's general rule for marine crustaceans is to buy as large an aquarium as you reasonably can, and it recommends at least 40 litres for smaller species of crabs and shrimps. At about 5 cm the Harlequin Shrimp is a small crustacean, but volume still matters: more water gives you more margin for the waste from its starfish meals and makes readings easier to hold steady.

Filtration

A filter is essential in any marine set-up. OATA describes three workable approaches: live rock with sufficient water flow, an internal or external filter, or a sump-based system. A protein skimmer is well worth adding, because it removes dissolved organic waste before that waste breaks down into more harmful substances. The RSPCA's aquarium welfare guidance explains the biology behind this: a working biological filter hosts beneficial bacteria that convert toxic ammonia into nitrite, which is also toxic, and then into nitrate, which is safer.

Equipment checklist

• A marine filter: live rock with enough water flow, an internal or external filter, or a sump.
• A protein skimmer to remove dissolved organic waste.
• A heater and thermometer that hold the aquarium steady within 24–26°C.
• A hydrometer or refractometer for salinity.
• Test kits for ammonia, nitrite, nitrate and pH, plus carbonate hardness, calcium and magnesium in a reef system.
• Live or artificial rock, arranged to give cover.

Rockwork and cover

Marine crustaceans need very little décor, but OATA treats live or artificial rock as essential. Rock provides grazing surfaces for many species and, more importantly for this shrimp, somewhere for a freshly moulted animal to hide while its new shell hardens. Arrange it so that there are sheltered gaps the shrimp can back into, while leaving enough open view for you to check that it is feeding.

A mature system, not a new one

Add the shrimp only to an aquarium whose filter has fully matured. OATA explains that the beneficial bacteria in a filter need to increase every time more livestock is added and feeding increases, and that stocking too quickly causes new tank syndrome: ammonia and nitrite rise to unhealthy levels and invertebrates can become ill or die. A starfish-eating shrimp brings both a new animal and a new source of waste, so it belongs near the end of a stocking plan rather than at the start.

Water chemistry and stability

OATA publishes suggested water parameters for marine crustaceans, noting that the group is usually undemanding of water chemistry and that the figures are a general guide rather than a profile of any one species. It also advises that a reef aquarium may need some values altered to suit more sensitive animals. Use the table below as the planning range for your Harlequin Shrimp, and aim above all for steady readings.

Why ammonia and nitrite matter so much

OATA stresses that crustaceans can be stressed by even the smallest amounts of ammonia and nitrite, which may then cause them to develop various diseases. That is why the table asks for zero rather than low readings. Test for ammonia, nitrite and nitrate as a matter of routine, and check salinity, temperature and pH as well, so that you notice drift before the shrimp does.

A simple testing routine

Reading the other values

Nitrate is safer than ammonia or nitrite, but OATA still sets a ceiling of 50 mg per litre for the group, and regular partial water changes are the usual way to keep it there. Carbonate hardness, calcium and magnesium belong to the same routine as in any reef system, so keep them inside the ranges above as part of your normal testing.

Moulting and the soft-shell days

Like every crustacean, the Harlequin Shrimp has a hard outer exoskeleton that it sheds as it grows. OATA points out that it is common to find empty shells in the aquarium, so a cast shell on the sand is a normal sign of growth rather than a lost shrimp. After shedding, the new exoskeleton takes a couple of days to harden, and the animal will often hide during that time.

Those soft-shell days are when cover matters most. A shrimp that has just moulted is at its most vulnerable, which is why OATA treats rock as essential décor for crustaceans: it gives freshly moulted individuals somewhere to hide. Resist the urge to move rockwork to look for a shrimp that has gone quiet after a moult.

Moulting problems to watch for

• difficulty moulting, or an old exoskeleton that is only partly shed
• a soft-shell condition that goes on much longer than a couple of days
• a clear change in how often the shrimp moults

If you see any of these, test the water first and look at the rest of the health checklist in the routine care section.

Arrival and the first days

Your shrimp is hand-packed by our team, bagged in pure oxygen inside an insulated poly box, with a heat pack when the weather calls for it, and it travels with a licensed live-animal courier. We email you the tracking number and the confirmed delivery date so you know when to be in. Someone needs to be at the address to receive the parcel, because live animals cannot be left unattended, and it should be opened and inspected on the day it arrives.

Before delivery day

• Check that ammonia and nitrite read zero and that salinity and temperature sit where you normally keep them.
• Have the first starfish arranged, so food is ready once the shrimp has settled.
• Make sure the rockwork offers cover near the front of the aquarium, where you will be able to watch the shrimp.

Unpacking and acclimatising

1. Start a continuous unboxing video while the parcel is still sealed and the outer box is visible, and keep filming in one take as you open it, until the shrimp can be seen inside its sealed bag.
2. Look at the shrimp through the bag before anything else is disturbed.
3. Float the sealed bag in your aquarium for 20–30 minutes before releasing the shrimp.
4. Release the shrimp gently into the aquarium, and never pour the bag water into your tank.

Acclimatise slowly and don't be tempted to hurry any of these stages.

If something has gone wrong

Contact us on the day the shrimp arrives with your order number and the unboxing video showing the sealed parcel being opened; WhatsApp is the fastest route. We'll arrange a replacement or refund. The full conditions are set out on our delivery and Live Arrival Guarantee page.

The video matters because our licensed live-animal courier may request continuous unboxing evidence from us when we raise a claim, and because it shows the shrimp's condition before anything was disturbed. That keeps claims quick, clear and fair for genuine customers. The same page has short clips from our own fishroom on unpacking and acclimatising, which are worth watching before the parcel arrives.

The first days in the aquarium

Once it is released, give the shrimp time to find its way around the rockwork before you judge how it is doing. Offer its first starfish once it has settled, then watch whether it starts to feed. Keep other new additions for later, because OATA advises increasing livestock only slowly so that the filter bacteria can keep pace.

Routine care and health checks

Good husbandry is what keeps a crustacean healthy, and a small, steady routine does most of the work.

Water changes

OATA strongly recommends a partial water change of 25% at least once every week. A siphon is useful for lifting solid waste out of the gravel or sand at the same time, and with this shrimp that includes any fragments left from its starfish meals.

Filter and skimmer care

• Check and clean filters regularly so that they don't block.
• If filter media needs cleaning, do not run it under the tap, because any chlorine or chloramine present may kill the beneficial bacteria living in it.
• Instead, rinse the media lightly in the tank water you have taken out during a partial water change, which keeps bacterial losses down.
• Clean the protein skimmer regularly so that it keeps performing well.

Health checks

Every shrimp has small quirks of its own, but OATA's list of changes to watch in marine crustaceans makes a useful checklist for spotting trouble before it becomes serious:

• Movement: reduced activity, long periods of inactivity, difficulty walking or swimming, loss of co-ordination, unusual movement or repeated attempts to leave the water.
• Colour: turning darker or paler than normal.
• Temperament: a change in behaviour, or hiding more than normal outside the days after a moult.
• Condition: damage to the exoskeleton, legs, claws, antennae or eyes, lesions, discolouration, white or fluffy growths, or the loss of limbs.
• Moulting: the problems described in the moulting section above.
• Feeding: reduced intake of starfish, or no interest in food at all.

If you notice one of these changes, test the water straight away, because OATA links even small amounts of ammonia and nitrite to stress and disease in crustaceans. If the readings are good and the shrimp still seems unwell, get in touch and tell us what you have seen.

Choosing safe companions

Compatibility for the Harlequin Shrimp comes down to two questions: what it will eat, and what might eat it.

Starfish

Every starfish in the aquarium is potential food. Its diet is starfish and nothing else, so an ornamental sea star kept for display is exactly what the shrimp is looking for. Never add this shrimp to an aquarium holding a starfish you want to keep. A starfish that goes in as food is a different matter, and that is its intended role.

Fish

OATA advises that marine crustaceans will generally mix with fish considered reef-safe, while fish that are not reef-safe are likely to prey on them and should not be kept with them. Take that seriously with a small shrimp that spends part of its life soft-shelled after each moult. Choose calm, reef-safe fish, and leave out anything known to hunt crustaceans. Because its hunting is aimed at starfish, fish are not on its menu.

Corals and reef aquariums

Corals are not part of this shrimp's diet, so it can live in a reef aquarium once the starfish question is settled. On wild reefs it even reduces coral losses, because shrimps attacking a crown-of-thorns starfish cut down how much coral that starfish eats. Keep in mind OATA's point that a reef aquarium may need some water values altered to suit its more sensitive inhabitants.

Crabs, lobsters and hermit crabs

OATA describes crabs and lobsters as opportunistic scavengers that may prey on slow-moving aquarium inhabitants, so mix them carefully with a shrimp this small, particularly around moulting time. Hermit crabs should always have ample food and plenty of spare shells, which stops them attacking snails for their shells.

Signs that a companion is causing trouble

The health checklist in the care tab can also point to trouble with a tank mate. A shrimp that suddenly hides far more than normal outside the days after a moult, or that shows damaged legs, claws or antennae, may be under pressure from a tank mate. Watch the aquarium closely for a few days, and if one animal is clearly responsible, separate them before the shrimp is injured further.

Mixing with other invertebrates

Marine crustaceans vary widely in their compatibility, and OATA's advice is to check each combination before introducing a new crustacean. If you are planning a mixed invertebrate aquarium around this shrimp, check the specific animals you have in mind with us before you order.

Reef aquarium or dedicated set-up?

Both can work well, and the better choice depends on what else you keep and how closely you want to follow the shrimp's feeding.

In an established reef aquarium

• Corals are safe from the shrimp itself, and a mature reef usually offers the stable water and rockwork it needs.
• Every starfish in the system is at risk, so a reef that relies on ornamental sea stars is the wrong home.
• Dense rockwork and a busy stock list make it harder to see whether the shrimp is feeding and to find leftover starfish.
• Any fish that is not reef-safe is likely to prey on it, so check the whole stock list before the shrimp goes in.

In a dedicated aquarium

• You can watch feeding closely and lift out leftovers without disturbing a reef.
• Nothing else in the tank is at risk from its diet, and you choose every companion around it.
• It still needs full marine filtration, live or artificial rock and a fully matured filter, exactly as a larger reef would.
• A smaller volume gives less margin for waste, so testing after each new starfish becomes even more important.

Keeping one shrimp or two

In the wild, harlequin shrimps live in pairs, and many keepers would like to recreate that. Each purchase is a single shrimp, and because sex isn't guaranteed, two shrimp ordered together can't be promised to be a male and female. Plan around the animals you actually have rather than expecting a pair to form.

Whether you keep one or two, food is the limit. Two shrimp will get through more starfish than one, so be confident your supply can feed both before you add a second. Plenty of rockwork matters too, so that each shrimp has somewhere to retreat, particularly when one of them has just moulted.

Harlequin Shrimp questions answered

How big does a Harlequin Shrimp get?

It reaches about 5 cm in length. We don't quote a dispatch length, so the shrimp that arrives may be smaller than that adult size; plan your aquarium around the full size.

What size aquarium does it need?

OATA recommends at least 40 litres for smaller species of crabs and shrimps and, as a general rule, the largest aquarium you can reasonably provide. For a Harlequin Shrimp it must also be a mature marine system with live or artificial rock for cover.

How many should I keep together?

In the wild, Hymenocera picta lives in pairs rather than groups. At home the real limit is food: your starfish supply has to feed every shrimp you keep, so keep only as many as that supply can sustain.

Is the Harlequin Shrimp suitable for beginners?

No. It needs a mature, stable saltwater aquarium and eats only starfish, so it suits experienced marine keepers who can keep a supply going. Newer keepers are better served by an adaptable reef shrimp that takes prepared food.

What does a Harlequin Shrimp eat?

Starfish, and nothing else. Wild shrimps prefer smaller, more sedentary starfish and commonly attack the crown-of-thorns starfish. Pellets, flakes and frozen crustacean foods are no substitute.

What temperature and pH does it need?

OATA's guidance for marine crustaceans as a group is 24–26°C, pH 7.9–8.3, salinity 1.023–1.026 and 8–12°dKH, with ammonia and nitrite at zero. Treat these as a planning range for the group rather than a tuned target for this shrimp, and keep readings steady.

Is it aggressive, and will it nip fish?

The Harlequin Shrimp hunts starfish, its only food, so fish are not its prey. The bigger risk runs the other way: fish that are not reef-safe are likely to prey on marine crustaceans.

Which animals can live with a Harlequin Shrimp?

Reef-safe fish generally mix well with marine crustaceans. Leave out fish that are not reef-safe and any starfish you want to keep, and add crabs or lobsters only with care, as they may prey on slow-moving tank mates.

How does it arrive alive in the UK?

We hand-pack each order in a bag of pure oxygen inside an insulated poly box, with a heat pack when the weather calls for it, and a licensed live-animal courier carries it. Film a continuous unboxing video from the sealed parcel, float the sealed bag for 20–30 minutes, then release the shrimp without adding the bag water. Contact us the same day, with your order number and the video, if anything is wrong.

Sources and further reading

• World Register of Marine Species: Hymenocera picta, for the accepted name, the synonym Hymenocera elegans and the family Palaemonidae.
• Wikipedia: Hymenocera, for natural history: range, adult size, life in pairs and the starfish diet.
• OATA: How to look after marine crustaceans, for water parameters, aquarium set-up, moulting, maintenance, health signs and compatibility.
• RSPCA: aquarium environment, for filtration and the nitrogen cycle.