Ugh! Vibrio is indeed nasty stuff, sir, and I have a great sympathy for anyone dealing with an outbreak of marine ulcer disease.
Heat stress is one of the triggers for Vibrio infections and I always see a spike in such cases from home hobbyists this time of year due to summertime heat waves.
Heat stress is especially debilitating and dangerous for seahorses due to a number of reasons (Olin Feuerbacher, pers. com.). For one thing, elevated temperatures can have a very detrimental effect on the immune system of fishes. This is because many of the enzymes and proteins involved in their immune response are extremely temperature sensitive (Olin Feuerbacher, pers. com.). Some of these protective enzymes can be denatured and inactivated by an increase of just a few degrees in water temperature (Olin Feuerbacher, pers. com.). So when seahorses are kept at temperatures above their comfort zone, their immune system is compromised and they are unable to fend off diseases they would normally shrug off.
At the same time heat stress is weakening the seahorse’s immune response, the elevated temperatures are increasing the growth rate of microbes and making disease organisms all the more deadly. Research indicates that temperature plays a major role in the regulation of virulence genes (Olin Feuerbacher, pers. com.). As the temperature increases, virulence genes are switched on, so microorganisms that are completely harmless at cooler temperatures suddenly become pathogenic once the water warms up past a certain point. Thus both the population and virulence of the pathogens are dramatically increased at higher temperatures (Olin Feuerbacher, pers. com.).
This is true of Columnaris and certain types of Vibrio. At cool temperatures these bacteria are relatively harmless, but at elevated temperatures they become highly contagious, virulent pathogens that kill quickly.
In short, it’s doubly important to keep seahorses at the proper temperature. Because of the reasons mentioned above and the fact that water holds less and less dissolved oxygen as it warms up, seahorses generally tolerate temps at the lower end of their preferred range much better than they handle temperatures at the upper limit of their range.
Unfortunately, Sam, I don’t know of any medications that can eradicate the pernicious and persistent Vibriosis infections from a reef system. When it is detected in its early stages, it can be treated successfully using potent antibiotics such as chloramphenicol, but these can also have a devastating impact on the biological filtration, resulting in spikes in the ammonia and nitrite levels and water quality problems that would be a nightmare in a reef tank with live corals. Some of the antibiotics can even tell the symbiotic zooanthellae in the coral polyps.
But if you contact me offlist, I can send you more detailed information than is possible on a discussion forum like this, Sam, so if you send me a brief e-mail, I may be able to be of more help. You can reach me at the following e-mail address:
In the meantime, here is some additional information regarding marine ulcer disease and some of the treatment options you can consider, Sam:
MARINE ULCER DISEASE, A.K.A. ULCERATIVE DERMATITIS, A.K.A. HEMORRHAGIC SEPTICEMIA, A.K.A. “FLESH-EATING BACTERIA”
Marine ulcer disease is a particularly nasty type of infection that most hobbyists have come to know as “flesh-eating bacteria,” and indeed it can often be attributed to bacteria, most notably gram-negative Vibrio or Pseudomonas species (Giwojna, Nov. 2003). Vibrio in marine fish is the equivalent of the Aeromonas bacteria that plague freshwater fishes (Dixon 1999; Basleer 2000), causing external hemorrhagic ulcers (bloody lesions). Vibriosis is probably the most common bacterial infection of captive seahorses and one of the most difficult to eradicate from your system. Vibrio bacteria are motile gram negative rods, which measure about 0.5 X 1.5 micrometers (Prescott, 2001). When grown on suitable media they appear as shiny, creamy colored colonies (Prescott, 2001).
Marine ulcer disease or hemorrhagic septicemia can manifest itself in a number of forms. The most common of these are the external hemorrhagic (bloody) ulcers, which appear as localized open wounds on the body (Dixon, 1999). It may be helpful to think of this condition as a form of skin rot. The first symptoms are usually small, discolored areas of skin that often become red and inflamed (Giwojna, Nov. 2003). These may become large bloody spots or lesions (the characteristic ulcers) as the disease progresses, leading to sloughing of the skin and localized swelling (Giwojna, Nov. 2003). (I have found that many times hobbyists have a tendency to dismiss these ulcers as “heater burns,” especially when they appear on the flanks or pouch of the seahorse, and to delay appropriate treatment on the basis of this misdiagnosis. Avoid this all-to-common mistake!) In severe cases, the underlying musculature also becomes infected, and the rapid tissue erosion that can result is one of the most alarming aspects of ulcer disease. At this advanced stage, all too often, the infected fish can longer be saved (Giwojna, Nov. 2003).
Badly infected fishes may develop a distended, fluid-filled abdomen due to internal bacterial infection (septicemia) of the kidneys, liver or intestinal tract (Dixon, 1999). This disrupts the normal circulation of the blood and lymph, causing fluids to accumulate in the intestine and abdominal cavity (Dixon, 1999).
The most dangerous form of hemorrhagic septicemia occurs when the bacteria spread internally and become septic, infecting the blood (Dixon, 1999). The bacteria release toxins into the bloodstream, making it the most virulent of these infections (Dixon, 1999). This insidious form of the disease does not produce the telltale external ulcers, and acute infections can kill quickly with little warning due to the lack of outward signs (Dixon, 1999). Affected fish become listless and lethargic (Dixon, 1999), which may be hard to pick up on with seahorses. Respiration is rapid and seahorses usually darken in color and go off their feed. These behavioral indicators are especially difficult to detect in seahorses due to their lazy lifestyle and habit of changing colors frequently. Seahorses may succumb to the acute form of this disease before the aquarist realizes anything is amiss, and hobbyist often ascribe such mysterious losses to Sudden Death Syndrome.
In seahorses, this disease sometimes takes the form of bilateral edema of the periorbital tissue (Bull and Mitchell, 2002, p19). The eyes themselves are not affected, as in popeye or Exopthalmia; rather, the tissue around both eyes swells up. The eyes are thus unaffected but are encircled by rings of swollen tissue. Hobbyists have described this condition to me by saying that their seahorse had developed “doughnut eyes.” These characteristic doughnut eyes are often accompanied by swelling of the soft tissue around the tube snout (Bull and Mitchell, 2002, p19). Some cases develop this peculiar facial edema as well as the usual skin ulcers and tissue erosion (Bull and Mitchell, 2002, p19).
Hemorrhagic septicemia or marine ulcer disease can be a very stubborn and difficult infection to treat, especially when it is due to Vibrio and the disease is acute or advanced. However, if the condition is detected early and treatment is begun when the discolored patches of skin or other symptoms are first noticed, antibacterial agents are often helpful (Giwojna, Nov. 2003). The professional aquarists treat this disease aggressively, using bivalent Vibrio vaccines, immunostimulants such as a beta-glucan, and injections of antibiotics (Bull and Mitchell, 2002, p19).
For the most part, such measures are beyond the grasp of we home hobbyists. We must make do by treating the affected specimens in isolation using wide spectrum antibiotics such as chloramphenicol, enrofloxin (brand name Baytril), tetracycline antibiotics (i.e., tetracycline or oxytetracycline) if and only if they can be a minister orally, gentamicin sulfate, doxycycline, kanamycin, neomycin sulfate, sulfonamide or streptomycin. In mild cases that are detected early, Furan2 or Nitrofuracin Green can sometimes also be helpful. As with other bacterial infections, lowering the water temperature during the course of treatment can help a great deal. This is your best course of action when you are confident that the problem is due to a bacterial infection, such as Pseudomonas or Vibriosis (Giwojna, Nov. 2003).
Chloramphenicol is the treatment of choice. It can be given orally or used as a bath (Prescott, 2001c). Therapeutic baths lasting 10-20 hours are administered in a chloramphenicol solution consisting of 40 mg per liter of water (Prescott, 2001c). If the seahorse is still eating, the chloramphenicol can also be bioencapsulated by gut loading feeder shrimp or ghost shrimp with flake food soaked in the antibiotic solution. Even if the affected seahorses does not eat, feeding medicated shrimp to its tankmates is a good way to help prevent this contagious disease from spreading to the healthy seahorses (Prescott, 2001c).
All things considered, Sam, I would say that chloramphenicol (i.e. Chloromycetin) is the treatment of choice for marine ulcer disease (i.e., flesh-eating bacteria) and most Vibrio infections, in general. It is effective both as a bath for prolonged immersion or when administered orally. If the affected seahorse is no longer eating, then administering the chloramphenicol to the treatment tank would be a good option for you if your other seahorses develop any symptoms of this disease.
The treatment protocol for Chloramphenicol or Chloromycetin is as follows:
Chloramphenicol can be used to treat Vibriosis at 40 mg/ litre of water (which comes out to about 150 milligrams per gallon) in a bath for 10-20 hours. It is important to watch the quality of the water, and if it starts to become turbid, the water must be changed. It is best to treat in a separate tank. In stubborn cases, a series of such baths may be necessary to resolve the problem, in which case a complete water change should be performed before the medication is redosed.
Chloramphenicol can also be used as an additive to the feed, if the fish are still eating (all too often in a major infection they will refuse to eat, but this treatment may be most useful in preventing the horizontal spread of the infection). When used as an addition to the feed use 500 mg per 100 gram of feed. (In the case of seahorses, the flake food medicated with chloramphenicol in this way would first be bio-encapsulated in live feeder shrimp, which would then in turn be fed to the seahorses.)
If you do obtain the chloramphenicol, be sure to be very careful when handling it. Remember, in a few rare individuals exposure to chloramphenicol can cause a potentially fatal side effect (aplastic anemia). These are rare cases and almost always involve patients who were being treated with the medication, but I would use gloves when handling it as a precaution and if you crush up tablets of chloramphenicol, be very careful not to inhale any of the power.
Because of this side effect, which affects one in 100,000 humans, chloramphenicol is no longer available as a medication for fishes and can therefore be all but impossible for the home hobbyist to obtain.
It can still be obtained from National Fish Pharmaceuticals (see the following link) but only in relatively large amounts:
Baytril is another good antibiotic for treating ulcerative dermatitis and tail rot, but it is a prescription medication that you would need to obtain from your family Vet. It would be your next best option if you cannot obtain the chloramphenicol.
Baytril (Enrofloxacin) is a powerful new broad-spectrum antibiotic that increasingly used to treat infections of the urinary tract, skin, prostate, gastrointestinal system, liver, ears, and lungs in humans. It is affective against both gram-negative and gram-positive bacteria and is widely used in aquaculture to treat marine fish. It belongs to a relatively new class of antibiotics called fluoroquinolones, which are effective against a wide variety of bacteria, and is now being used in the aquaculture industry to treat bacterial infections in valuable fish. In liquid form, enrofloxin (Baytril) can be administered either by injection at around 10mg/kg bodyweight e.o.d. or as a bath at 30ppm for 1 hour daily for 5 days.
The Baytril can also be administered orally by tube feeding it to the seahorse, which is helpful when the seahorse is not eating, but it is a stressful procedure for the seahorse. Here are the instructions for administering the Baytril orally, again courtesy of Ann at the org:
ENROFLOXACIN Oral Dosage and Preparation Instructions
Active Ingredient: Enrofloxacin
Indication: bacterial infection
The following information is based on the most commonly available tablet sizes for Enrofloxacin/Baytril
available in the US and abroad and an average sized seahorse of approximately 10 grams.
Tube feed the seahorse 0.1mg of Enrofloxacin once a day for 10 days.
Day 1 – 10 of Treatment
• Crush 1/4 of a 68mg or 50mg tablet into a fine powder.
• Use a mini-blender or small hand-blender to thoroughly mix the powder with marine water. Mix 1/4 of a
68mg tablet with 85mL of marine water. Mix 1/4 of a 50mg tablet with 62.5mL of marine water.
• Fill a small syringe with 0.5mL of the solution.
• Tube feed the seahorse just as if you were force-feeding the pony to provide nutritional support.
• Throw out the unused Enrofloxacin and marine water solution. You will need to make new solution daily
because Enrofloxacin breaks down quickly in saltwater causing it to become completely ineffective by the
Enrofloxacin is available only by prescription from a veterinarian.
Enrofloxacin International Version – Tablets are produced in 15mg, 50gm, 150mg, & a 2.5% injectable solution
Enrofloxacin US Version – Tablets are produced in 22.7mg, 68mg, 136mg, & a 2.27% injectable solution
If you are able to ascertain the exact weight of your seahorse you may want to adjust the dosage as
necessary to get the most benefit from the medication. In such an instance you would dose Enrofloxacin
at 0.01mg of the medication per gram of body weight.
A veterinarian who works regularly with small exotics will be familiar with the proper way to dilute
injectable Enrofloxacin solution to fit your needs.
If you do not have access to prescription medications such as chloramphenicol or enrofloxacin (Baytril), then you should consider using tetracycline or oxytetracycline instead, since they are readily available to hobbyists, but ONLY if they are administered orally. (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. Obviously, this is only an option if the affected seahorse is still eating, which is often not the case.
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 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.
If the seahorse is not eating, you can therefore not administer the antibiotics orally, consider treating the pony with gentamicin or a combination of doxycycline + kanamycin, as explained below. That is something you could consider, Sam, but it is an expensive option and you may find it difficult to obtain both the doxycycline on the kanamycin sulfate in pure form at a therapeutic dosage. It is very unlikely that you will be able to obtain any chloramphenicol or Baytril (enrofloxacin), without a prescription. That means that the combination of kanamycin + doxycycline may be the best choice for you:
In short, your next best alternative may be to obtain doxycycline and kanamycin from National Fish Pharmaceuticals and use them together to form a synergistic combination of antibiotics that is often very effective in treating Vibrio infections. (DO NOT attempt to use doxycycline and kanamycin in your main tank, because they will destroy the beneficial nitrifying bacteria that carry out biological filtration, and your display tank will no longer be able to support any life, until it has been completely cycled from scratch again.)
USE: broad spectrum antibiotic derived from oxytetracycline. Use for both gram-positive and gram-negative bacterial disorders, including fin and tail rot, septicemia, and mouth rot. Unlike tetracycline antibiotics, it will not be deactivated by the high pH levels found in marine aquaria. Works in a similar manner to chloramphenicol.
DOSAGE: add 1/4 teaspoon per 20 gallons, every 24 hours for 10 days. Do a 25% water change before each treatment.
This is a potent broad-spectrum, gram+/gram- aminogylcoside antibiotic. It is wonderfully effective for aquarium use because it is one of the few antibiotics that dissolves well in saltwater and that is readily absorbed through the skin of the fish. That makes it the treatment of choice for treating many bacterial infections in seahorses. Kanamycin can be combined safely with certain other antibiotics such as doxycycline or neomycin (as well as metronidazole) to further increase its efficacy. Like other gram-negative antibiotics, it will destroy your biofiltration and should be used in a hospital tank only.
USE: gram-negative bacterial infections and resistant forms of piscine tuberculosis (mycobacteria). Works especially well in saltwater aquariums.
DOSAGE: add 1/4 teaspoon per 20 gallons. Treat every 24 hours and perform a 25% water change before each treatment. Treat for 10 days. (When treating piscine tuberculosis, treat for 30 days.)
Both the doxycycline and kanamycin can be obtained online from National Fish Pharmaceuticals at the following URL:
In summation, Sam, I would recommend isolating the affected seahorses just as you have done and treating the rest of the seahorses’ and fish (that are not already too far-gone) aggressively with antibiotics in a treatment tank. The following antibiotics have proven to be effective in treating such infections when they are detected early (I have listed them in order of preference):
Chloramphenicol (i.e., Chloromycetin)
enrofloxin (i.e., Baytril)
tetracycline or oxytetracycline (but only if they can be administered orally)
Doxycycline hydrochloride + kanamycin sulfate
Good luck treating this dread affliction and saving some of your seahorses, Sam. E-mail me offlist ASAP!
Pete Giwojna, Ocean Rider Tech Support