Pete Giwojna

Dear John:

First of all, sir, let me just say that it sounds like you have done a remarkable job of nursing your ailing Hippocampus erectus seahorse through a series of major crises. You are obviously very dedicated to your seahorses and it sounds like your male H. erectus is a real fighter who has demonstrated amazing recuperative abilities.

And you deserve major kudos for hanging in there with your ailing pony and breaking a hunger strike of two weeks due to illness not once, but on two separate occasions! Well done, indeed!

Your instincts on those occasions were very good, John. Ordinary Vitamin B12 intended for human consumption and purchased from a drugstore or pharmacy, health food store, or even a supermarket can sometimes work wonders as an appetite stimulant and restorative when a seahorse has stopped eating. For the sake of the readers who may find themselves dealing with a similar situation at some time, John, can you very briefly outline how you administered the vitamin B12 so successfully in your case, sir? (Thank you for sharing your experience on the forum!)

I don’t know how helpful I can be in this situation, but I would be happy to share my thoughts on the matter with you and to suggest a possible treatment regimen. It appears that you’re dealing with a bacterial infection of some kind, since the antibiotics have been able to clear up the lesion on a couple of occasions. I don’t know why this problem keeps recurring, John. I cannot say if it is because the bacteria involved have developed resistance to the antibiotics you been using, or if the antibiotics have been having a bacteriostatic effect and suppressing the infection, but only as long as the antibiotic was being administered, allowing the infection to get out of control again when the treatment regimen was over. Or you may be dealing with a mixed infection involving more than one type of pathogen.

But in my experience, the bacteria that are most often responsible for the sort of tissue erosion you describe in seahorses are species of Vibrio or Pseudomonas bacteria. Those are tough infections to cure, and Pseudomonas in particular is very good at developing resistance to antibiotics, but they often respond to antibiotics that are especially effective against gram-negative bacteria.

You mentioned that you have his feeding under control right now, John, and in that case, I would suggest that you consider treating your seahorse with tetracycline or oxytetracycline administered orally by gut loading adult brine shrimp with medication. Tetracycline antibiotics are readily available to the home hobbyist from aquarium shops and fish stores and they would be a good choice for you because there is normally no problem at all with marine fish having resistance to the tetracyclines because of the simple fact that they cannot be used in saltwater so marine fish have typically never been exposed to these types of antibiotics before.

(The tetracycline antibiotics are useless in saltwater, because calcium and magnesium bind to the medications and deactivate them when the pH is 7.6 or above.) So the only way tetracycline antibiotics can be used effectively with seahorses is to gutload feeder shrimp with the medication or, alternatively, to soak frozen Mysis in the proper concentration of the medication, and then feed the medicated Mysis to the seahorses.

If you can obtain live adult brine shrimp, the feeder shrimp can be gut loaded with the tetracycline antibiotics and then fed to the seahorses. In that case, 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 the ailing seahorse.

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 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 15-30 minutes and then feed the medicated shrimp to your seahorses immediately. (Don’t let your pumps and filters "eat" all the brine shrimp!)

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 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 gallon of water.) Or in the case of the Tetracycline MS, use one 500 mg packet per gallon of freshwater.

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 as long as necessary. 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. 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 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.

If the seahorse stops eating again, John, and you can therefore not administer tetracycline antibiotics orally, consider treating the pony with gentamicin instead:

Gentamicin is one of the most potent of all antibiotics against gram-negative bacteria. It is effective when dissolved in saltwater and is readily absorbed into the bloodstream of the fish so it can be used in a hospital tank as follows:

Gentamicin Sulfate Powder 100%

USE: probably the most powerful gram-negative antibacterial on the market today. Effective in fresh and saltwater aquariums. Only a single dose is usually required. One of the few drugs that is absorbed into the bloodstream through the gills.

Dosage: 1/4 teaspoon per 40 gallons. Only one dose is necessary. Treat one time and leave in water for 7-10 days. If water changes are done, replace the medication according to how much water was changed.
(National Fish Pharmaceuticals)

Gentamicin can be obtained online, without a prescription, from National Fish Pharmaceuticals at the following URL:

In short, John, to address the possible problem of disease resistance, I would suggest bioencapsulating tetracycline so that it can be administered to your male seahorse orally by gut loading feeder shrimp with the medication, or, if that’s not feasible, then administering a regimen of the gentamicin in your hospital tank would be the next best option.

Best of luck nursing your plucky seahorse through this ordeal and curing this infection once and for all.

Pete Giwojna

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