Harlequin Shrimp

Dear arcprolife:

Harlequin shrimp belong to a group of colorful, very fancy shrimp in the genus Hymenocera whose diet consists solely of starfish. They are commonly known as Elegant shrimp, Harlequin shrimp, Painted shrimp, Clown shrimp, and Dancing shrimp and are quite beautiful, having pinkish or purplish polka dots and saddles against a white background. They are 1-2 inches long with large, flattened claws that resemble flower petals, which they use to display to one another. To me, they always look like animated orchids. They are shy, gentle, and completely harmless (except to starfish) so they should certainly do well with seahorses. They occur as mated pairs and are one of my favorite shrimp.

Two species are available — Hymenocera elegans, which tends to have purplish or violet polka dots, and Hymenocera picta, which tends to have pinkish polka dots. I have kept both species and found them fascinating. They are rather pricey for shrimp but well worth the cost as long as you can provide them with adequate water quality (low nitrates and no copper!).

Despite their ghoulish dining habits, water quality is not an issue when the gaudy Harlequin shrimp are feeding due to the manner in which they consume their prey. They prefer to feed on starfish with tube feet but they don’t kill them out right. Rather, they overturn the hapless starfish and then immobilize it by daintily eating its tube feet first, so that they can dine on the crippled starfish at their leisure. When they are done with the tubefeet, they will usually proceed to work on its arms next. Given their amazing ability to lose arms and regenerate as long as their body disc is left intact, the unfortunate incapacitated starfish remains alive right up until the bitter end. One meal last them a long, long time, so a pair of harlequins does not need to be fed often.

If you have a chance to acquire a pair of Harlequin shrimp, go for it! They are beautiful and really fascinating to observe. But as with all shrimp, they do best in well-established aquariums with stable water quality, so they are not good candidates for newly cycled tanks.

Happy Trails!
Pete Giwojna

Dear arcprolife:

Yes, sir, if your aquarium has been up and running for six months then it should be stable enough for Harlequin shrimp (Hymenocera spp.) or other decorative shrimp. You will be feeding them with starfish that you add to the aquarium every couple of weeks, so as long as you can maintain optimum water quality and stable conditions, they should do fine. When you bring the Harlequins home from your LFS, drip acclimate them over a period of several hours for best results.

As for the starfish, the Harlequin shrimp must be able to overturn the sea star in order to control it and expose their tube feet, which they will normally feed on first in order to immobilize their prey. If the starfish is too large, it may be too heavy or cling to the substrate too tenaciously for the ornate little Harlequins to upend. When that’s the case, the starfish can thwart the Harlequins and evade them. A good-sized chocolate chip starfish may be too big and powerful for them to overcome.

Harlequin shrimp could certainly handle any of the Linkia or Fromia starfish, which are no threat to your seahorses in any case, but you don’t need to serve up the colorful, exotic sea stars for their dinner, which would be a costly waste. I always fed my Harlequins with the common, ordinary, nondescript sea stars from my LFS that were always cheap and readily available. They are just the common brownish to tannish or orangeish seastars that come in to any pet store that keeps marine fish in shipments from Florida or the Caribbean or wherever, often as unwanted add-ins or throw ins. Look for a regular starfish of average size, say with an arm span 3-4 inches across, and they should fill the bill nicely. (Avoid the serpent starfish or brittle stars — you want a common sea star with tubefeet.)

Even though it’s only intended as prey for the Harlequin shrimp, drip acclimate the sea star to your seahorse tank over a period of hours so that it stays lively and healthy. Harlequin shrimp aren’t scavengers. They don’t eat dead, decaying starfish are other decomposing organic matter — they prey only on living starfish, which they consume in such a manner that they remain alive so their food stays fresh.

The Harlequin shrimp will track down and overpower a suitable starfish fairly soon after it it’s added to their tank, but they are cautious and deliberate when they do so. The pair of shrimp work together and pry up one or more of the sea star’s arms, which they use as leverage to overturn their victim. Once the sea star has been upended so they can control it, they will often take it back to a sheltered spot where they can feed on it at their leisure, beginning with the tubefeet on the underside of its arms. If the starfish is crawling on the glass beyond their reach, it is perfectly safe. They can only handle starfish when they are on the bottom of the aquarium.

Best of luck finding a beautiful pair of Harlequin shrimp and inexpensive, suitable starfish for them to feed upon.

Happy Trails!
Pete Giwojna

Dear arcprolife:

Yes, sir, you really need to choose between one or the other. If there is a particular starfish that you want to keep in your aquarium, then you need to do without the Harlequin shrimp. Or, if you have your heart set on a mated pair of Harlequin shrimp (Hymenocera sp.), then you really need to do without a decorative starfish.

The harlequins won’t discriminate between inexpensive feeder starfish that you offer them for their meals and a fancy, expensive starfish that you would like to keep as an attractive addition to the aquarium. Sooner or later the fancy starfish is bound to attract the attention of the Harlequin shrimp and become a victim, no matter how well fed that you try to keep them.

I should explain that I have never tried that particular experiment, sir — I have never tried keeping Harlequin shrimp and having any starfish in the tank on other than those intended to be their meals. I don’t know if they would be at all inclined to "stockpile" starfish when they are abundant, or if they are content to dine on one starfish at a time. But since their method of attacking and immobilizing the starfish allows them to incapacitate the starfish but still keep it alive and healthy, they certainly could tackle more than one sea star when the feeding was good, clip off and consume all of their tube feet, and then have two helpless, completely immobilized starfish to feed upon at their leisure. Or they may decide the fancy starfish was more appealing as a meal than the cheap sea star you offered them as dinner at some point.

I just don’t think that would be a workable arrangement. At some point, the decorative starfish is bound to fall prey to the Harlequin shrimp.

Best of luck finding colorful, interesting tankmates for your seahorses, arcprolife!

Respectfully,
Pete Giwojna