Re:bristleworm damage to seahorse’s snout

Dear Tom:

Ouch! I’m sorry to hear that your big Brazilian stallion came out on the wrong end of a close encounter with a bristleworm. I have heard of this sort of situation on a few different occasions, and you need to concentrate on two things under the circumstances – preventing secondary infections from the embedded spicules and keeping the seahorse eating despite the irritation and swelling from the urticating spines. One thing that is sometimes helpful in achieving both goals is to feed the affected seahorse with soft-body live adult brine shrimp that have been gutloaded with antibiotics. The soft-bodied adult brine shrimp are relatively easy to slurp up and swallow, which encourages the seahorse to eat when tempted by the live food, and the antibiotics are often most effective when they can be administered orally in this way.

For immediate first aid, I have no idea as to whether the tape will work well for removing the embedded spicules from a seahorse’s snout, but it does sometimes work well for removing them from your hands and fingers. I will trust your judgment as a first-hand observer on that one, Tom. The hydrocortisone is worth a try as a topical application, but use it sparingly and be careful not to get it in the seahorse’s eyes or gills. The hydrocortisone could be soothing but I don’t know if it will have time to help or if it will immediately get rinsed off in the saltwater.

Under the circumstances, I would recommend treating your H. reidi prophylactically in the main tank by administering tetracycline orally via gutloaded adult brine shrimp. This would be a very stress-free method of medicating the stallion because he can be treated in the main tank where he is the most comfortable without handling him or disturbing him, and your ponies will be treated with live food for a welcome change of pace. Tetracycline is effective when administered orally and I find that adult brine shrimp (Artemia spp.) work best for gutloading or bioencapsulating the antibiotic for a number of reasons.

Both the adult brine shrimp and the tetracycline are readily available to most home hobbyists from their local fish stores and at very reasonable costs. For now, suffice it to say that the tetracycline cannot be used in saltwater, and adult brine shrimp are pretty much the only feeder shrimp that tolerate freshwater long enough to be effectively gutloaded with the medication.

Tetracycline is a good broad-spectrum antibiotic but it is only useful for treating marine fish when it is administered orally by adding it to their food. Adding tetracycline to saltwater is useless because it binds to calcium and magnesium in the water and is deactivated when the pH of the water is 7.5 or above. The best way to administer the tetracycline would be to bioencapsulate it in live adult brine shrimp and then to feed the medicated shrimp to your seahorses.

Many times the most effective way to administer antibiotics orally is by bioencapsulating or gutloading them in live shrimp, which are then fed to the seahorses. The easiest way to gutload antibiotics is to bioencapsulate them in live adult brine shrimp (Artemia spp.), as described below. The recommended dosage of antibiotic for this varies between 100-250 mg per liter or about 400-1000 mg per gallon of water. Stay within that range and you should be all right.

In the case of tetracycline, I recommend using 500 mg per gallon of freshwater (or 125 mg per quart of freshwater) for bioencapsulating the antibiotic in adult brine shrimp. Tetracycline is a photosensitive drug, so keep the container of freshwater covered to shield it from the light or in a relatively dark area of the room while you are gutloading the brine shrimp.

If the antibiotic you are using comes in tablet form, crush it into a very fine powder (you may have to use a household blender to get it fine enough) and dissolve it in freshwater at the dosage suggested above. Soak the adult shrimp in freshwater treated with the antibiotic for a minimum of 15-30 minutes and no more than 2 hours and then feed the medicated shrimp to your seahorses immediately. Be sure to provide gentle aeration using coarse bubbles to the enrichment container while you are gutloading the adult brine shrimp to keep them healthy and active. (Don’t let your pumps and filters "eat" all the brine shrimp!) Gutload a new batch of adult brine shrimp each day to feed to your seahorses, and continue for 7-10 days.

The brine shrimp are soaked in freshwater, not saltwater, because in theory the increased osmotic pressure of the freshwater helps the antibiotic solution move into their bodies via osmosis. But in fact nobody knows for sure whether the antibiotic is diffusing into the brine shrimp or they are ingesting it in very fine particles (brine shrimp are filter feeders and will take in whatever is suspended in the water with them) or whether the brine shrimp merely become coated with the antibiotic while they are soaking in it. But that’s not important — all that really matters is that gut-loading adult brine shrimp with medications this way is effective.

The antibiotics I would recommend for gutloading in your case are tetracycline or oxytetracycline. Tetracycline is widely available for aquarium use, so you should easily be able to get a product at your LFS in which the primary ingredient is tetracycline, such as Maracyn-TC by Mardel Labs or Tetracycline MS by Fishvet. These products generally include 250 mg capsules or tablets of tetracycline, or packets of 500 mg tetracycline powder, which would make it easy for you to determine the right amount to add to 1 gallon or 1 quart of freshwater in which to soak your brine shrimp to gutload them with the antibiotic. (Just add two of the 250 mg capsules or crushed up tablets — i.e., 500 mg worth — of the tetracycline to a gallo of water.) Or in the case of the Tetracycline MS, use one 500 mg packet per gallon of freshwater when gutloading the shrimp.

A quart container or 1 liter bottle is a convenient size to use when gutloading a portion of live adult brine shrimp to feed to your seahorses. In that event, the proper dosage to use is 125 mg of tetracycline per quart or liter.

Although tetracycline and oxytetracycline generally work very well when administered orally, they are all but useless when used as bath treatments for marine fish. This is because the calcium and magnesium in hard water or saltwater bind to tetracycline and oxytetracycline, rendering them inactive (Yanong, US Dept. of Agriculture). In addition, tetracycline and oxytetracycline are photosensitive drugs and will decompose when exposed to light. So these drugs are very useful for seahorses when they are administered via bioencapsulation, but they are utterly ineffective when added to the water in a saltwater aquarium are hospital tank (Yanong, USDA). This is another reason why you must soak the live adult brine shrimp in freshwater when gutloading them with tetracycline or oxytetracycline.

Gutloading the adult brine shrimp in freshwater has several advantages. First of all, it disinfects the brine shrimp (the osmotic shock in going from concentrated saltwater to freshwater will kill off any protozoan parasites the brine shrimp may have been carrying). Secondly, the freshwater increases the effectiveness of the gutloading process by allowing some of the medication to enter the body of the brine shrimp via osmosis. And gutloading the adult brine shrimp in freshwater saves the hobbyist from having to mix up fresh saltwater every day in order to medicate the adult Artemia. Just use dechlorinated/detoxified freshwater as described above, and everything should go smoothly. But the most important reason that you gutload the adult brine shrimp in freshwater when you are using tetracycline or oxytetracycline is that these medications will be deactivated in saltwater and rendered useless if you attempted to bioencapsulate the medication in adult brine shrimp that are in saltwater.

I would feed your seahorses their fill of adult brine shrimp gutloaded with tetracycline once a day for 7-10 days. Gutload a new portion of the adult brine shrimp each day for the seahorses’ first feeding of the day when they are the most hungry. So that would be a total of 7-10 feedings, one per day, using adult brine shrimp gutloaded with the tetracycline. Give the seahorses a second feeding of frozen Mysis enriched with Vibrance later in the day. The Vibrance includes beta glucan as an active ingredient, which is in an immune stimulant that will help the seahorses to fight off any infections.

It is impossible to determine precisely what dosage of medication each individual fish ingests when gutloading, but the tetracycline antibiotics are very safe and you really cannot overdose a seahorse using this method of treatment. Feeding each seahorse its fill of shrimp gut-loaded with tetracycline for 7-10 days assures that they receive an effective dose of the medication. As long as each seahorse is getting its share of the medicated brine shrimp every day during the treatment period, you needn’t be concerned if one of the ponies is eating more than the others.

In short, Tom, the feeder shrimp I find that work best for gutloading or bioencapsulating medications are adult brine shrimp (Artemia species). As you know, I prefer adult brine shrimp (Artemia spp.) for gutloading for a number of reasons. For one thing, adult Artemia are inexpensive and readily available to the home hobbyist. Secondly, soaking live adult brine shrimp in a solution of the medication in freshwater is by far the simplest and most convenient way to bioencapsulate meds, as we have discussed previously. Thirdly, a much wider range of medicines are effective when bio-encapsulated in live brine shrimp than can be used effectively as bath treatments for marine fish because they adult brine shrimp tolerate freshwater so well while they are been gutloaded.

Bioencapsulating the adult brine shrimp in freshwater thus greatly increases the range of antibiotics you can use for gutloading. Many antibiotics are ineffective when used as baths in saltwater because they don’t dissolve well in hard water at a pH > 8.0, or aren’t absorbed well through the skin and gills of fish, or because they combine with the carbonates in saltwater and are thus rendered inactive (tetracycline, for example), or all of the above. That is why the marine dose for most antibiotics is much stronger than the dosage recommended for use in freshwater, but increasing the dosage only partially counteracts these problems.

Soaking the brine shrimp in freshwater while they are bio-encapsulated with the medication also disinfects the adult brine because the osmotic shock in going from full strength saltwater to the freshwater kills any protozoan parasites the Artemia may have been carrying. And it increases the effectiveness of the gutloading because it allows some of the medication to move into the bodies of the adult brine shrimp via osmosis, assuring that they take up more of the medication.

With regard to eradicating the bristleworms from your aquarium, Tom, this is normally what I advise home hobbyists regarding these prickly polychaetes:

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 who 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, 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. A fairly effective way to reduce their numbers is to regularly trap large bristleworms after lights out along with keeping a young arrow crab 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 be used to help limit 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.

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.

Okay, Tom, that’s the quick rundown on bristleworms. If your aquarium does not house delicate invertebrates, it’s possible to completely eliminate the bristleworms by using an anthelminthic or deworming agent, but such chemicals can be hard on the invertebrates. Let me know what type of invertebrates you have in your seahorse tank and I will let you know if eliminating the bristleworms chemically might be a good option for you.

Best of luck resolving your bristleworm problem, Tom!

Respectfully,
Pete Giwojna