Harlequin shrimp pair

Harlequin Shrimp Care Guide

Harlequin shrimp (Hymenocera picta), in my opinion, are one of the most beautiful marine invertebrates in the world. Just take a look! They are mostly white with colorful spots all over their mantis-shaped body. In general, they grow to a maximum size of 2 inches. (Females come out significantly larger than males) The three most common reasons aquarium owners consider purchasing them are:

  1. Because they are gorgeous
  2. To clear up an Asterina starfish infestation
  3. To watch the shrimp’s amazing hunting behavior

Table of Contents: Harlequin Shrimp Care

Who wouldn’t want to leap at the chance to add one of these vibrant crustaceans to their reef aquarium? You have plenty of reasons to do so. But before you rush to the fish store to pick out your favorite, check out the links below. These invertebrates are specialist predators. Not sure what that means? Maybe you want to check out the care and feeding section. Better yet, maybe you should cruise through the entire article and make sure you’re not missing something critical in the care and management of harlequins. After all, they have some particular needs.

Harlequin shrimp on green starfish

Harlequin Shrimp Natural Habitat

Harlequin shrimp are found on rubble piles outside of coral reefs from Hawaii and throughout the Indo-Pacific region. There are regional color differences, with some specimens having white bodies and maroon to purple spots with blue outlines. In contrast, those found closest to Hawaii have a white-to-cream-colored body with bright pink to magenta-colored spots.

In their natural habitat, the shrimp form breeding pairs that rarely stray more than a few inches from each other. The pairing is thought to be both for the purposes of mating and the added benefit of having a hunting partner. And that’s bad news if you’re a starfish. (More on that in a minute)

Unlike some shrimp species, harlequins remain active and hunt during the day. And this remains part of their behavior in marine tanks. It adds to their popularity with aquarists.

Harlequin shrimp shot from the front

Harlequin Shrimp Lifespan

A few websites report that harlequin shrimp live for about 7 years. Anecdotal reports online from hobbyists suggest about 2-3 years once introduced to the tank. (This relates to some of the difficulty with their management)

Tank Set-Up for Harlequins

These shrimp tend to be shy at first and need a safe place to hide. Often times they will pick a cave and turn that into their lair. They use the hideout for resting and eating. The pair (or your lone harlequin) will drag prey off and eat in privacy. So you need to make sure you offer places for them to do so.

Harlequin shrimp need water temperatures between 72-84F/22.2-28.8C and are very susceptible to water chemistry and salinity changes. Water changes need to match both chemically and in temperature. They cannot handle copper or nitrates in the water (chemicals commonly used to treat parasite infestations in fish). Of course, if you have any experience with crustaceans, in general, you already know the “no copper” rule.

Harlequins are also vulnerable to strong currents and will shy away if your tank has too much flow. A quick scan of forum posts discussing these colorful crustaceans show a number of posts from people who lost their fish to their powerhead filters. Finding circulation and filtration systems that don’t create too much of a current is an absolute must for keeping harlequins happy and healthy. A gyre pump may be best for these shrimp if you intend to keep them in a larger reef tank.

Harlequins require mild currents

However, because of their size and delicate structure, you may want to consider keeping them in a nano tank. They’ll be more secure (and therefore visible). Then they can remain the main focus. (And you picked them up for their stunning patterns and hunting behavior, anyway, right?)

Are Harlequin Shrimp Reef-Safe?

Yes, harlequin shrimp are considered reef-safe – with one big exception. They eat echinoderms (starfish). So they’re not compatible with starfish, but they leave corals and fish alone.

Molting

Harlequin shrimp, like all shrimp, shed their exoskeletons as they grow; their hard outer shell doesn’t grow with them.

As they grow, a new shell develops under the old one. When it’s ready to grow, the old shell splits open, and they emerge within their new shell.

Occasionally an old shell will come off in such a perfect piece that some aquarists think the shrimp is dead and lying motionless on the bottom of the tank. The problem is often made worse because a freshly molted shrimp knows that new exoskeleton is soft and vulnerable to predators. So they hide for a few hours until it hardens. So don’t jump to conclusions too quickly if you find a lifeless carapace in your tank.

A fresh molt lacks the vibrant color patterns of your hale and healthy harlequin. Instead, it will look dull and opaque. Go ahead and leave the molt in place, though. The shed exoskeleton provides a healthy source of nutrients to the shrimp and the surrounding tank environment. So feel free to leave it where it lies and watch the resulting “natural” dance.

Harlequin shrimp and starfish

Harlequin Shrimp Compatibility

Harlequin shrimp can be kept with smaller fish and many kinds of crabs. Other shrimp can be an issue, though, as all shrimp tend to be territorial.

Harlequin shrimp don’t have a lot of natural predators in the wild. However, in a tank setting, they are likely to be picked on by any fish that eats shrimp. So it goes without saying (although I guess I am saying it) it isn’t wise to keep harlequins with fish known to eat shrimp, like dwarf lionfish or hawkfish

Wrasses, in particular, can also be a problem, but any large fish can pose a potential threat. Even if the larger fish don’t stop to eat the shrimp, the threat of imposing predators can keep them in hiding. 

Since their natural food are starfish (more on that in a bit), don’t keep them with any decorative starfish or sea urchins that you don’t want to see eaten.

Pair of harlequin shrimp

Care and Feeding of Harlequin Shrimp

Harlequin shrimp only eat starfish (and in times of absolute desperation, sea urchins). Specifically, they go after the tube feet of starfish. There is NO alternative food source you can easily entice them with. A pair of harlequins goes on the hunt for starfish. They’re able to smell their prey, even if the echinoderm is hidden. It’s this hunting behavior that attracts plenty of aquarists to add the crustaceans to their aquariums.

Once the shrimp find a starfish, they stand on top of it to immobilize the echinoderm. Then they flip it over to access those precious tube feet. As soon as the starfish is on its back, the pair will begin to drag it away to their lair and begin feasting upon it. (Grisly, huh?)

Want to witness the process firsthand? Take a look at the YouTube video below!

A single harlequin shrimp can make ONE starfish last up to two weeks. Generally speaking, they start eating at the point of one starfish “leg” and work their way through the tube feet toward the center. Some hobbyists have reported their harlequins bringing algae into the cave to force-feed the starfish to keep it alive and fresh for their dining! (Talk about barbaric!)

Some starfish species shed their legs to get away from predators. They do this when targeted by harlequins. (Beats having your tube feet devoured over a couple of weeks!)

Because of their very particular tastes, harlequin shrimp get quite expensive to keep. However, chocolate chip starfish are some of the lowest-cost options for aquarists to consider stocking, and even those come in at $9-$12 each.

Harlequin Shrimp and Asterina Starfish

Yes, harlequin shrimp eat Asterina starfish – and just about any other species of starfish you might find or purposefully add to your tank. (In fact, they only eat starfish and often starve in home reef tanks) Asterina can turn into pests in some aquariums. That’s great for your harlequins – until they eradicate the infestation. Then you need to pick up the ball and run with it to continue the shrimp’s care. As they ARE day-hunters, you have a little bit of warning and can watch to see how they’re doing – outside of the cave, anyway.

As you’ll see in the YouTube video below, harlequins can’t get enough of Asterina starfish!

Preventing Starvation

Since harlequin shrimp have voracious appetites and will only eat starfish, you need a plan to ensure you will always have food available. Here are a few thoughts (each with their own level of reasonability and humaneness):

  • Let everyone you meet in the hobby or at a store, know that you’re happy to take their leftover Asterina starfish.
  • Try to get Asterina starfish to set up shop in your tank.
    • Asterina stars are generally considered pest species, often hopping a ride into your tank with your newest arrivals from the local fish store (LFS).
    • To harlequin shrimp, they are a buffet. A pair of hungry harlequins could polish off 15 of these little guys a day. That means using them as your sole feed is probably unrealistic. But if you’ve already got a problem with them killing your coral, harlequin shrimp could be the answer.
  • Set up a starfish farm (Ew, gross)
    • The idea is to keep a handful of starfish that can quickly regrow their arms in small separate tanks (they are often cannibalistic). Then, remove a leg from each day on a rotating basis to feed to your shrimp.
    • If you have enough, they will regenerate their arms before it’s time to give up another one.
      • Aside from having to cut the legs off a live animal every day, the downside of this operation is the space and resources necessary to keep all the starfish separate and alive.

Harlequin shrimp feeding on a starfish

  • Stock up on starfish.
    • If you ever find a sale on starfish, you probably want to buy them in bulk.
    • This could cut down on some costs if you are willing to find space in your freezer or have a tank for them.
    • It’s important to note that frozen starfish DO rot faster in a tank. So feeding smaller pieces more often will be necessary.

Harlequin Shrimp Reproduction

Harlequin shrimp prefer to live in breeding pairs and spawn every month or so.

Raising them from their larval stage in a home tank has been met with limited success thus far. However, recently, a commercial aquarium company managed to raise 500 harlequins from larvae to adulthood. Hopefully, there will be more successes, and a methodology for home propagation will be available soon.

Harlequins have stunning colorsFor More Information

Harlequin shrimp are gorgeous. It is amazing to watch their hunting behavior and how adeptly they can disarm (pun intended) an unsuspecting starfish. But raising them in a reef tank comes with many challenges. Their dietary needs aren’t for the faint of heart (or those on a budget). Regardless of how you source your starfish, be ready for clean-up duty. Harlequin shrimp eat starfish feet. They won’t eat the whole starfish.  So the rest of the body will be left in your tank…to rot. (Ugh.)

Most clean-up crews won’t eat the outer bits of the stars, either, meaning that regularly removing decaying starfish from the tank is a chore that accompanies harlequin shrimp ownership. 

What do you think? Would you consider keeping one? Share your thoughts in a comment below!

This YouTube video will walk you through everything you need to know about caring for harlequin shrimp (if you’re determined to bring one home):

If you would like to learn more about great shrimp species that are easier to care for, check out:

What about other awesome aquarium predators?

Harlequin shrimp care guide

References

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