Reply To: Coral banded shrimp

Pete Giwojna

Dear Michael:

Coral banded shrimp (Stenopus hispidus) are well armed and their feisty, pugnacious temperament has earned them the nickname or common name of Boxer Shrimp, which is well justified.

In nature, they may perform a beneficial service by grooming the larger fish such as green morays or overgrown groupers. But in the aquarium, with small reef fishes, they tend to “clean” any small fish they can get their claws on right down to the bone. They have very poor vision and operate mainly by touch, aided by their umbrella of feelers, and their sense of smell, which is very good. They have an unfortunate tendency to try to bear hug just about anything within reach that moves or gives off an intriguing aroma. I would hate to be the seahorse that wandered within hugging distance of one of these coral bandits, and in the confines of the aquarium, that’s something that’s likely to happen, sooner or later…

The yellow (Stenopus cyanoscelis) and gold (Stenopus zanzibaricus) coral banded shrimp do tend to be a bit smaller in size as well as less pugnacious, but I have never tried keeping either of those shrimp species with seahorses, sir, so I can’t say for certain how well they get along with our peaceful ponies…

In short, sir, if you are concerned about the bristleworms in your seahorse tank and were therefore hoping that some of the compatible shrimp could help to control them (which they may indeed due to a limited degree, although banded coral shrimp (Stenopus hispidus) are the best shrimp for controlling bristleworms, but are a little too pugnacious for a seahorse setup), then I do think it is a good idea for you to take some additional steps to reduce the bristleworm population in your seahorse setup because the bristleworms can present a risk to the seahorses under certain conditions.

As you know, up to a point, most bristleworms are perfectly harmless or even beneficial to the aquarium. It is only in those unusual cases where the errant bristleworms become very large or very numerous that they present any danger to seahorses, as discussed below, and it sounds like the bristleworms in your seahorse tank may now have become too abundant and/or too large to ignore.

To be more specific, I would recommend using a combination of trapping and biological control to eliminate the risk of bristleworms, Michael. The biological control can be accomplished using bristleworm predators that are compatible with seahorses, such as chocolate chip starfish, cleaner shrimp, and perhaps an arrow crab or two of the right size. Please read through the following information which will explain how to do so, sir:


For hobbyists’ purposes, these polychaetes can be characterized as either sedentary or sessile species — i.e., harmless tube builders and filter feeders that stay in one place — or errant species that wander about in the aquarium and scavenge or hunt). The sedentary or sessile bristleworms are completely harmless, whereas the wandering or errant bristleworms species are only dangerous under exceptional circumstances.

In my experience, there are three circumstances during which the errant bristleworms become problematic in the aquarium — when they become too large, when they become too numerous, and when they are the notorious but very rare fireworms rather than the ordinary, run-of-the-mill, garden-variety bristleworms. Errant bristleworms have powerful jaws and specimens larger than two or three inches in length can deliver a painful bite. (Some species even have poisonous bites, although they’re not normally dangerous to humans; the bite is only about as bad as a bee sting.)

Virtually all of the errant bristleworms are literally bristling with urticating spicules that penetrate the skin and break off on contact, giving these prickly pests their common name. The embedded spicules are always irritating and the wounds they cause tend to become easily infected, and in the case of the rare but dreaded fireworms, the poisonous spicules are extremely painful. For this reason, it’s a good idea to wear protective gloves when working in an aquarium that’s known to house bristleworms, especially when you are rearranging the live rock.

Here is an excerpt from Mike Noreen’s Bristleworm FactSheet that explains a little more about how the wandering or errant bristleworms can sometimes cause trouble in the aquarium:

<open quote>
3. Errant bristleworms.
The real problem childs in tanks. They are ugly, move in an unnerving manner, can pack nasty poisonous bites and/or poisonous bristles, and may eat things the aquarist would not like them to eat. In general appearance they resemble centipedes (although the ‘legs’ are not true legs, and they
are not related to centipedes), and are always present in all tanks with live rock or live sand. They are of varying colour, size and disposition, and a great number of families and even greater number of species are found in aquaria. It is very common for errant polychaetes to be opportunists — eating algae, scavenging, or killing small invertebrates as they find them. Despite their omnivorous habits the vast majority of species are totally harmless in a reef tank. A very few species may, however, cause problems.

4. The Bad Boys.
Errant bristleworms cause problems in two ways: either by becoming so big that they can attack things they normally would not be able to harm (i.e., fish or aquarists fingers), or by being predators/parasites on valuable inhabitants in the aquarium.

Bad because of size: Basically a bristleworm larger than, say,
two-three inches can deliver painful bites, and conceivably kill fish, shrimp etc. Some species also have poisonous bites, and although I’ve never heard of anyone dying of a bristleworm bite, there’s no doubt they could seriously inconvenience a sensitive person (normally a bite from
a poisonous species, such as a Glycera, is comparable to the sting of a wasp). Use caution (and/or tweezers) when dealing with a large worm.

Bad because it’s a specialized predator/parasite: Actually very few bristleworms are parasites, and none on vertebrates, so the fish are usually safe (except for very large very hungry predatory worms). Some species do eat corals, and may cause problems. The most known coral-eating
species is the Fireworm.

5. The Fireworm:
The Fireworms are a group of coral-eating worms from the Caribbean, common in shallow waters. In general appearance a fireworm is fat (fatter than an earthworm) reddish-brown, with prominent tufts of white-to-green bristles. They can multiply rapidly, and can in a short time kill all corals in a tank. They have gotten their names from having poisoned bristles, which cause skin irritation. Handle with care.

Various methods have been suggested to remove Fireworms. These include: commercially sold traps, mechanical removal with tweezers, putting something tasty (e.g., shrimp meat)
in old nylon stockings in the tank overnight. The worms become entangled in the nylon, and can be removed in the morning. If I sound somewhat vague on fireworms, that’s because I’ve never even seen an actual fireworm.
<Close quote>

In short, Michael, I think it would be appropriate to take steps to thin out your bristleworm population at this time in order to prevent them from becoming too numerous or growing too large, sir. Here is what I normally advise hobbyists in that regard:

Bristleworms In the Seahorse Tank

In general, bristleworms are benign, even beneficial inhabitants of a seahorse tank that perform a useful service as scavengers. But when their numbers get out of control or they grow too large, there comes a point when an overabundance of bristleworms becomes problematic as far as seahorses are concerned. That point is generally when the exploding population of bristleworms become too large and aggressive at feeding time, actively seeking out the frozen Mysis even during daylight hours, no longer content with cleaning up leftovers, and begin invading the feeding station. Too many bristleworms lingering too long at the feeding station brings them in direct contact with the hungry seahorses that come to the lunch counter for their favorite food as usual. The galloping gourmets may accidentally brush up against the encroaching bristleworms, or even attempt to perch on them, and they may get a snootful of bristles when snicking at the same mysid a bristleworm has taken an interest in. Even if the seahorses don’t inadvertently snick at them, the bristleworms may shed a few of their irritating spicules while they are at the feeding station, and the hungry seahorses can then accidentally ingest such loose spicules when slurping up frozen Mysis. Captive bred seahorses are aggressive eaters that are accustomed to slurping up food from the bottom, and it seems at times this may also lead them to strike at baby bristleworms. I’ve also heard a few reports of seahorses that snicked up a tiny bristleworm and got them lodged in their snout or throat. It’s unclear in these cases whether the bristleworm was accidentally sucked up while the seahorse was targeting a piece of nearby Mysis or whether the seahorse actually mistook the tiny worm for something edible and deliberately struck at it, but this is another potential danger the seahorse keeper should be aware of.

I have seen pictures of seahorses with bristleworm spicules embedded in their tails and snouts as a result of such close encounters. These injuries are usually minor, easily treated by removing the spicules and administering antibiotics orally via gut-loaded shrimp to prevent secondary infections, but the more bristleworms there are, the more likely such incidents and problems are to occur.

I have seen a few seahorse tanks that were overrun by them to the extent that the bulk of the total biomass in the aquarium consisted of bristleworms! When that happens, they are detrimental simply because of their effect on the water quality. Under certain circumstances, the total metabolic activity of the countless bristleworms may have a greater impact on the nitrogen cycle that all of the seahorses and their tankmates.

So when you start to see bristleworms swarming the food station, it is a good idea to start thinning them out. You might consider using a form of biological control to reduce the bristleworm population. For instance, I have been told that chocolate chip starfish have a taste for bristleworms, and are sometimes insatiable bristleworm predators that are active at night and which can clear an aquarium of bristleworms when all other measures have failed (Dr. Randy Morgan, pers. communication).

Likewise, Arrow crabs (Stenorhynchus seticornis) are predatory on bristleworms. Large arrow crabs can sometimes be problematic for seahorses, but in my experience they get along well together. You might want to try a small-to-medium-sized Arrow Crab, which will predate small bristleworms and help keep their numbers in check.

Although arrow crabs will happily devour any bristleworms they can catch, they won’t eradicate them entirely from your aquarium. Too many of the bristleworms always remain inaccessible to them within the rockwork and sand for that, but a small to medium-sized arrow crab or two can help control the bristleworm population.

Six line wrasse and certain other wrasse species also eat bristleworms.

However, the problem with using wrasse, cleaner shrimp, or arrow crabs for this purpose is that all of those bristleworm predators also love frozen Mysis, which they will find in abundance in a seahorse tank, and therefore they almost always have little or no interest in hunting bristleworms and are an aquarium with seahorses. It’s simply much easier for an arrow crab or fish or shrimp to scavenge up leftover Mysis than it is for them to hunt down, overpower, and devour bristleworm, particularly bristleworms of any appreciable size.

A fairly effective way to reduce their numbers is to regularly trap large bristleworms after lights out along with keeping a young arrow crab or two along with some cleaner shrimp to thin out smaller worms (providing there are no sessile invertebrates in the tank the crabs could harm).

In my experience, small to medium-sized arrow crabs are safe with large seahorses and can sometimes be marginally helpful in limiting the number of bristleworms in your tank. But if you want to try this, you don’t want to pick out the biggest, baddest, bruiser of an arrow crab to do the job! Go with a smaller specimen, keep a close eye on it, and be prepared to replace it with a smaller individual after it molts once or twice. They grow fast and can nearly double in size after each molt. And you can also try chocolate chip starfish as bristleworm predators instead.

Remember there are always exceptions to every rule, and large crustaceans are never completely trustworthy. Even the most harmless and seemingly inoffensive crabs can cause trouble under certain circumstances. For example, not long ago I heard from a hobbyist that had been keeping a decorator crab in his seahorse tank. All went well at first and there were no problems of any kind for months until, for no apparent reason, the crab suddenly began to quite deliberately amputate portions of the seahorses’ tails. It was not attacking the seahorses as prey or attempting to eat its mutilated victims, it was merely methodically harvesting portions of their anatomy with which to adorn itself! It was simply doing what all decorator crabs do — snipping off and gathering bits and pieces of its immediate environment to attach to itself as a form of natural camouflage. It just goes to show, with crabs you can never be sure how things are going to work out…

I would characterize arrow crabs (Stenorhynchus seticornis) as opportunistic omnivores. I have kept them in a number of my aquaria over the years, including a few seahorse tanks, without any problems. They never bothered my Hippocampus erectus at all, but they can be hard on sessile invertebrates in general and I certainly wouldn’t trust them with dwarf seahorses. Nor would I trust them with a small bottom-dwelling fishes like gobies. In my opinion, it’s best for the seahorse keeper to avoid arrow crabs because they are likely to do more harm than good in a seahorse tank and are largely ineffectual in controlling bristleworm in any case.

First and foremost, bristleworms are best controlled by trapping them. A number of bristleworms traps are available at aquarium outlets and can serve as the seahorse keeper’s first line of defense against these prickly pests. Here are some tips from Dee that explain the best ways she’s found for trapping bristleworms:

<Open quote>

I actually caught a bristle worm last night that’s massive!!! Only 4″ long but nearly 1/2″ wide! I used a trap for him. I wasn’t going for him. I knew there was a big one in my reef tank and had seen one about 7″ long. He was the one I was after. My hubby woke me up this morning to come see the one I did manage to catch.

Besides him though I’ve caught quite a few smaller ones as well. I like to check my reef tank about 1 1/2 hours after the lights have been shut off. Then when I find them I watch them as they flee from the flashlight and know where they are hiding. I set the traps right next to their hidey holes and catch them. If they are really narrow the traps aren’t that good. They can get back out very easily so you can’t wait until morning to check the traps. You need to check them
periodically through the night, if a small worm is in the trap, empty it then don’t wait till morning or he’ll be gone. Even the huge one I just caught managed to get into a hole about 1/8″ in diameter to the food chamber.

I’ve had better success with nylons. I buy knee high nylons and at night drop a rock or two in the toe along with some food. Then I set the toe area right near the holes. When they try to get the food, they get stuck in the nylons. In the morning I just pull it out of the tank and get rid of them.

I’ve also used a turkey baster a few times. If you can get into the tank quiet enough, they won’t really move, squeeze the ball and when you’re really close to the worm let go. The suction can be pretty good sometimes depending on where they are.


Question: Anyone out there with any great successes at catching and eradicating your tank of bristles without the use of drugs? This is important to me since I have an amazing Coco worm and a few other things planned for my reef that will be harmed by the so called “wormicides”. I’ve been using a trap with on and off success, actually caught about 13/night for the first few nights, but I’m not having much success catching the more cautious ones. I think there might only be one or two left but not able to coax them out.

The best bait for trapping bristleworms depends on what I have handy at the time 🙂

I found the brine shrimp and sometimes krill (both frozen) work well. I usually add some to either the trap or the nylons and then take a small container of water from my reef tank to thaw it out before putting either the traps or nylons in my tank.

I’ve got two more tricks for ya, First the turkey baster. It doesn’t really have a lot of suction power. Or at least I’ve never found one that the ball was on tightly. So I bought a new one and took the ball off. I wrapped the end with thick clear tape, same diameter as duct tape just clear tape. Then when I put the ball back on it was much tighter giving me much better suction.

Also, there is a different type of bulb that is very useful especially for small worms. They make them for babies noses and you can also get them anywhere they sell camera equipment. They are used to blow dust off camera lenses. They are a good size to fit in your hand snugly and have good suction. Again to make it better there is a small hole
in the bottom on the bulb. I used a piece of a silicone ear plug and covered the hole. Now I’ve got twice the suction and it works great!!

Even though the spout end looks small it really can suck up some good size worms.

Personally, I’m fascinated with the night time world of my tanks. I completely dewormed my rocks in my seahorse tank. But as for my reef tank, I kinda like having some bristle worms in there. They really do clean up a lot of stuff and in tiny little spaces where no one would ever think would need cleaning. But when I start finding portions of dead hermit crabs, I get a bit cranky. I still can’t kill them though.

I’ve still got the huge one alive and well and am trying to figure somewhere where I can put him so he can live. I’d love to watch him closer. I also get a bit cranky when I reach into a tank at night and don’t watch where I’m reaching. Oops! Got hit pretty hard by a fireworm one night from a brand new rock. Ended up pulling out three bristles and got a good sting that lasted 3 days.

Good luck catching your worms, once you start, you’ll get hooked on catching the little monsters 😉
<Close quote>

If the population of bristleworms isn’t too bad, Michael, they can also be thinned out very effectively simply by carefully winnowing out the largest specimens at night after lights out using a long-handled tweezers. It’s a good idea to wear protective gloves when doing this, since the spicules from these prickly pests are extremely irritating and large specimens can deliver a painful bite.

Hobbyists should be aware that overfeeding can greatly contribute to an overabundance of bristleworms. If you have been scatter-feeding or broadcast feeding your seahorses, you can really cut down on the excess Mysis that are available for the bristleworms to scavenge by target feeding your seahorses or training them to eat from an elevated feeding station. Cutting down on their food supply in this manner will naturally reduce the size and number of bristleworms in the aquarium.

Bristleworms can also be eradicated from the aquarium altogether by treating the tank with fenbendazole (brand name Panacur), which is a deworming agent commonly used to treat horses and livestock. It is safe for seahorses and will do a marvelous job of eliminating bristleworms, but it’s best to save this control measure as a last resort for the most severe cases because the fenbendazole can be harmful to live corals and certain snails, and because the massive die off of the entire bristleworms population can result in a dangerous ammonia spike.

Fenbendazole (brand name of Panacur) is an inexpensive anthelmintic agent (dewormer) used for large animals such as horses, and the de-worming granules can be obtained without a prescription from stores that carry agricultural products (e.g., farm and ranch equipment, farming supplies and products, veterinary supplies, livestock and horse supplies, livestock and horse feed) or via the Internet from places such as KV Vet Supply. The granular form of fenbendazole (horse dewormer granules 22.2%) is preferable to the paste for aquarium use, as the dosage of the granules is easier to regulate (Liisa Coit, pers. com.). It is available in packets of 5.2 grams or 0.18 ounces.

I would recommend you try trapping the bristleworms after dark, as described above, Michael, and adding a couple of chocolate chip starfish and/or smallish arrow crabs to your tank. If you can remove the larger specimens by trapping them, you should be able to control their numbers effectively, Michael.

Just don’t freak out about bristleworms and overreact at the sight of a few of the pests. Bristleworms are not public enemy number one — they are more of a problem for reef keepers than seahorse keepers, as a rule, and in most instances, they are harmless or even helpful residents of your seahorse tank. But if you want to play it safe, no one here will fault you for trapping the little buggers and terminating them with extreme prejudice.

Best of luck reducing your bristleworm population for the sake of your seahorses, Michael!

Pete Giwojna, Ocean Rider Tech Support

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