Re:Flesh-Erosion Disease

Pete Giwojna

Dear strataman:

No, sir, Aquarium Pharmaceuticals Pro Series Cure Ich is useful in treating Cryptocaryon irritans and other external parasites, but it will not be effective against marine ulcer disease (a.k.a. "flesh-eating bacteria"). Your seahorse has developed a serious bacterial infection and you will need to use powerful broad-spectrum antibiotics to treat this condition. The Cure Ich would be counterproductive in this case — stressful to the fish but not at all effective in controlling the bacteria.

Nifurpirinol may be marginally helpful but there are other antibiotics that are more appropriate when treating this dreaded disease. The bacteria most commonly associated with marine ulcer disease are Vibrio or Pseudomonas species. Some of the other antibiotics that have proven to be effective in treating such infections are listed below. In terms of effectiveness, I would rate them roughly as follows:

Chloramphenicol (i.e., Chloromycetin) either as a bath or administered orally

streptomycin, flumequine, and polymyxin B (all good choices but very hard to obtain)

Neo3 (neomycin sulfate combined with triple sulfa)

kanamycin as a bath (one of the few antibiotics that works well in saltwater and is absorbed readily through the skin and gills)

tetracyclene/oxytetracycline (can be effective but ONLY if administered orally)


(As you can see, sir, nifurpirinol would be far down the list but it is certainly better than nothing if it is the only antibiotic you have on hand.)

Remember, raising or dropping the water temperature just a few degrees can also make a huge difference when treating bacterial infections such as this. Likewise, here are Neil Garrick-Maidment’s observations on the importance of water temperature when treating a Vibrio infection:


I am not sure if it is of any help but I recently had a problem with vibriosis

in Hippocampus capensis coupled with a couple of gas bubbles in the end of the

tail. Having tried a number of treatments in the past that havn’t worked I took

a slightly more drastic approach this time and dropped the temperature from 23

down to 18 degrees C (64°F) having first isolated the infected animals into a separate

tank. I then left them like this for 4 weeks after which I increased the

temperature slowly up to 21 degrees C or 70°F (which it still is). After the second week

the vibriosis had gone completely (and has not returned) and the gas bubbles

were gone after the third week. In all the time the temperature was low the

animals reduced their feeding and it has now increased with the raising of the

temperature and they since gone on to have two broods of fry.

Best wishes,

Neil Garrick-Maidment

Seahorse Project Co-ordinator

Hippocampus erectus has an enormous range of the wild and can adapt to an equally wide range of temperatures, so if the affected seahorses are H. erectus, they would be perfectly comfortable at the same temperatures Neil used to cure his H. capensis, if you can possibly drop the temperature in your treatment tank that far. If not, just dropping the temperature a few degrees from normal can often make a huge difference when treating bacterial infections.

Finally, here’s a research paper I thought you might be interested in since it documents a case of mass mortality among hippocampus kuda due to a Vibrio infection, and discusses the antibiotics that were found to be effective against that strain of Vibrio (note that chloramphenicol was again found to be the most effective medication):

Vibrio harveyi causes disease in seahorse, Hippocampus sp.

E Alcaide1, C Gil-Sanz1, E Sanjuµn1, D Esteve1, C Amaro1 and L Silveira2

A mass mortality among cultured seahorses,

Hippocampus kuda and Hippocampus sp., occurred

in spring 1998 in Tenerife, Spain. Seahorses were

held together with tropical shrimps, Stenopus

hispidus, in glass aquaria supplied with 1000 L of

sea water at 25 °C. The water supply was conducted

between different tanks that contained various

marine species, such as octopus, Octopus vulgaris,

star®sh, Asterias rubens, sea-urchin, Paracentrotus

lividu, greater weever, Trachinus draco, grouper,

Epinephelus guaz and Canarian shrimp, Lismata

amboiens. None of these species was affected,

including the shrimps that shared aquaria with the

seahorses. Mortalities of seahorses were very high

(more than 90%), and the fish died in 3-5 days

after the first clinical signs appeared. Moribund

seahorses were microbiologically analysed and subsequently,

chloramphenicol was used as a bath

(30 mg L)1) to control the outbreak. The mortality

decreased after a few days of antibiotic treatment.

Diseased seahorses presented clinical signs similar

to vibriosis: external haemorrhages, and haemorrhagic

liver and ascitic fluid accumulation in the

intestinal cavity. A bacterium identified as Vibrio

harveyi was obtained in pure culture from samples

of skin haemorrhages, mouth and liver of all

moribund seahorses. The aim of this study was

to characterize the V. harveyi strains isolated from

diseased seahorse, and to confirm its pathogenicity

by means of experimental infection.

Samples from skin haemorrhages, mouth and liver

were analysed by streaking a piece of aseptically

obtained tissue onto tryptone-soy-agar supplemented

with 1% NaCl (TSA-1) and incubating at 25 °C

for 24±48 h. Pure cultures were obtained from all

samples. The isolated strains were Gram-negative

rods, motile, oxidase- and catalase-positive, sensitive

to the vibriostatic agent O129 at 150 lm and

fermentative. The isolates were first characterized

by API 20NE (BioMeÂrieux, S.A. France) strips,

which gave the same profile in all cases (7474445),

identi®ed by the database APILAB Plus

(BioMeÂrieux) supplied by the manufacturer as

V. vulni®cus, with a probability of 95.1%. Further

identification was achieved by colony hybridization

as previously described (Biosca, Amaro, Larsen &

Pedersen 1997), using an alkaline phosphataselabelled

oligonucleotide DNA probe (VVAP) specific

for V. vulni®cus, constructed from a portion of

the V. vulni®cus haemolysin±cytolysin (hlyA) gene

sequence (Wright, Miceli, Landry, Christy, Watkins

& Morris 1993). Positive and negative controls used

were V. vulni®cus ATCC 27562 and V. cholerae

ATCC 14035, respectively. All isolates were negative

in colony hybridization experiments, which indicated

that they were misidentified as V. vulni®cus.

Identification was continued by testing additional

biochemical characteristics as described by Biosca,

Oliver & Amaro (1996). On the basis of the results

obtained, the seahorse isolates were identified as

V. harveyi. They were almost identical to the type

strain of V. harveyi, except for growth at 12 °C and

luminescence (Table 1). Vibrio harveyi is a synonym

of V. carchariae (Pedersen, Verdonck, Austin, Austin,

Blanch, Grimont, Jofre, Koblavi, Larsen, Tiainen,

Vigneulle & Swings 1998), which is recognized as a

fish pathogen (Yii, Yang & Lee 1997). The present

strains differed from the type strain of V. carchariae in

swarming, production of urease, growth with 8%

NaCl and at 40 °C, and the utilization of sucrose,

arabinose, d-mannitol and l-citruline.

Cultures grown on TSA-1 were suspended in

sterile phosphate buffered saline (PBS) at pH 7.2 and

DO600 nmwas adjusted to 0.4. Aliquots of 0.1 mL

of this suspension were spread onto Mueller±Hinton

agar (Oxoid, Basingstoke, 2 UK), and antimicrobial

sensitivity tested using antimicrobial discs (Becton

3Dickinson, Pharmaceuticals, NJ, USA). The following

drugs were used: tetracycline (30 lg), flumequine

(30 lg), chloramphenicol (30 lg), oxolinic acid

(10 lg), trimethoprim-sulphametoxazol (25 lg),

nitrofurantoin (50 lg), oxytetracycline (30 lg),

erythromycin (15 lg), furazolidone (50 lg), gentamicin

(10 lg), kanamycin (30 lg) and polymyxin

B (300 U). Strains were sensitive to tetracycline,

flumequine, chloramphenicol, nitrofurantoin and polymyxin

B. Chloramphenicol and flumequine produced

the widest inhibition halos in the test plates.

The 50% lethal dose (LD50) test, with batches of

six seahorses per dose, were conducted by intraperitoneal

(i.p.) injection as previously described (Alcaide,

Amaro, TodolõÂ & Oltra 1999). Seahorse (mean

weight 4 g ®sh)1), were injected with 0.05 mL of a

bacterial suspension containing 107)102 cfu mL)1

(determined by plate counts on TSA-1), in PBS.

Sterile PBS was injected i.p. into seahorses as a

control. Mortalities were recorded daily for 14 days,

and were only considered positive if the injected

strain was recovered from assayed seahorses. The

LD50 as calculated by the method of Reed&Muench

(1938) was 4 ´ 103 cfu ®sh)1. Pure cultures of the

inoculated strains were re-isolated from liver and skin

haemorrhages of moribund seahorse. No mortality

was detected in the controls. Clinical signs appeared

12±24 h after i.p. injection and mortalities began

1±7 days post-challenge. The signs observed in

challenged seahorses reproduced those observed

during the outbreak. This result confirmed the role

of V. harveyi as the causative agent of the disease.

In the present work, an infectious disease affecting

seahorse, Hippocampus kuda and Hippocampus sp., is

described for the first time. The isolates from diseased

seahorse had the same morphological and biochemical

characteristics, and were identi®ed as V. harveyi

from comparison of their biochemical characteristics

with the type strain of the species. Vibrio harveyi is

a marine bacterium that causes luminous vibriosis

(Zhang & Austin 1999) and is an important

pathogen of cultured penaeid shrimp (Lavilla-Pitogo,

Baticados, de Cruz-Lacierda & de la PenÄa 1990;

Karunasagar, Pai, Malathi & Karunasagar 1994;

Liu, Lee, Yii, Kou & Chen 1996; Montero & Austin

1999). It has also been reported as an opportunistic

pathogen of common snook (Kraxberger-Beatty,

McGarey, Grier & Lim 1990), and has been isolated

from diseased marine fish such as Acanthopagrus

cuvieri (Saeed 1995), sea bream, Sparus aurata

(Balebona, MorinÄigo, Faris, Krovacek, MaÈnsson,

Bordas & Borrego 1995), and dentex, Dentex dentex,

cultured on the Mediterranean coast of Spain

(Company, SitjaÁ-Bobadilla, Pujalte, Garay, Alvarez-

Pellitero & PeÂrez-SaÂnchez 1999). Further studies are

in progress to characterize the virulence factors

involved in the pathogenicity of V. harveyi isolates.


This study was supported by grant GV-D-AG-02-

138-96, from the Conselleria de Cultura, EducacioÂ

i CieÁncia, Generalitat de ValeÁncia (Spain).

Journal of Fish Diseases 2001, 24, 311±313 E Alcaide et al. Vibrio harveyi outbreak in seahorse

All things considered, I would say that chloramphenicol (i.e. Chloromycetin) is the treatment of choice for most Vibrio infections. It is effective both as a bath for prolonged immersion or when administered orally. If the affected seahorses are no longer eating, then administering the chloramphenicol to the treatment tank would be a good option for you.

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 to 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 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 difficult to obtain. If you find that is the case, you might have better luck switching to kanamycin instead. A fish medication that includes kanamycin sulfate as its primary ingredient (e.g., KanaPlex) should be available from any well-stocked LFS:

Kanamycin sulfate

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 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.

For best results, it’s an excellent idea to combine the kanamycin with neomycin to further boost its efficacy, as described below:

Neomycin sulfate powder

USE: Gram-negative bacteria (Pseudomonas), piscine tuberculosis and other bacterial infections. Works well in freshwater or saltwater aquariums.

DOSAGE 1/4 teaspoon per 10 gallons of water. Treat every 24 hours with a 25% water change before each treatment. Treat for 10 days. For piscine tuberculosis, use for up to 30 days.

Neomycin is a very potent gram-negative antibiotic. Most of

infections that plague marine fish are gram-negative, so neomycin

sulfate can be a wonder drug for seahorses (Burns, 2002). As

mentioned above, it can even be combined with other medications such

as kanamycin or nifurpirinol for increased efficacy. For example,

kanamycin/neomycin is tremendous for treating bacterial infections,

while nifurpirinol/neomycin makes a combination that packs a heckuva

wallop for treating mixed bacterial/fungal infections or problems of

unknown nature. Keep it on hand at all times.

Neomycin will destroy beneficial bacteria and disrupt your biological

filtration, so be sure to administer the drug in a hospital tank.

If you obtained neomycin in capsule or tablet form rather than the powder, the standard treatment protocol is 250 mg/gal (66 mg/L) as the initial dose and 50% replacement (125 mg/gallon) thereafter with a daily 50% water change repeated for 10 days.

Kanamycin and/or neomycin sulfate can also be combined with various sulfa compounds. One that seems to work well is combining neomycin sulfate with triple sulfa. You may be able to get neomycin sulfate and triple sulfa compound at a well-stock LFS. If not, you can obtain both neomycin sulfate powder and triple sulfa powder from National Aquarium Pharmaceuticals. You can order them online at the following site:

Better yet, Neo3 is a broad-spectrum antibiotic consisting of neomycin combined with sulfa compounds to produce a potent synergistic combination of antibacteri, and you may be up to be able to obtain the Neo3 online from the following vendor:

If, for some reason, you have difficulty locating the kanamycin and neomycin or Neo3, you will surely be able to locate a fish medication based on tetracycline or oxytetracycline at your LFS. These medications are completely useless when added to the saltwater in a marine aquarium, since they bind with calcium and magnesium, but they have proven to be very effective in treating bacterial infections, including certain strains of Vibrio, when administered orally, as described below:

Tetracycline and oxytetracycline can also be used like Chloramphenicol as an addition to the feed, with the limitation as already mentioned that so often with Vibrio infections the fish will not eat. When attempting to use Tetracycline in the feed take 750 mg tetracycline HCL and mix same with 100 gram of feed. Use this mixture for at least one week, feeding twice daily in the morning and early afternoon. The dosages for oxytetracycline are exactly the same as for tetracycline. (Again, when treating , the flake food medicated with tetracycline/oxytetracycline in this way would first be bio-encapsulated in live feeder shrimp, which would then in turn be fed to the seahorses, as discussed below.)

Tetracycline is also 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 and is deactivated. 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 ailing seahorse, as explained below:

The best 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.

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, providing the ailing seahorses are still eating. 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. These products generally include 250 mg capsules or tablets of tetracycline, 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 four of the 250 mg capsules or crushed up tablets — i.e., 1000 mg worth — of the tetracycline to a gallon of water.)

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 quite ineffective when added to the water in a saltwater aquarium (Yanong, USDA). This is another reason why you must soak the live adult brine shrimp in freshwater when gutloading them with tetracycline or oxytetracycline.

Here is some additional information on marine ulcer disease that may give you a better idea of what you’re up against, strataman:


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 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, 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).

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, kanamycin, oxytetracycline(orally), neomycin sulfate, sulfonamide or streptomycin, or nifurpirinol. 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 prevent this contagious disease from spreading to the healthy seahorses (Prescott, 2001c).

The bacteria (Vibrio, Pseudomonas, etc.) that cause this dread affliction are highly contagious, so while the affected seahorses are being treated in isolation, you must also tend to your main display tank (Giwojna, Nov. 2003). The trick is to treat it without destroying your biofilter in the process.

A good place to start is to clean up and sterilize the main tank. Many health problems are associated with deteriorating water quality and hemorrhagic ulcers are no exception (Giwojna, Nov. 2003). If your primary biofiltration is provided by live sand and live rock, you can safely remove the equipment and as much of the décor (except the LS/LR) as possible and sterilize everything before returning it to the aquarium (Giwojna, Nov. 2003). Once the seahorses have recovered from their ordeal and are ready to be returned to the main tank, we want to make sure they benefit from pristine conditions and optimum water quality (Giwojna, Nov. 2003).

Even if the problems with your kuda is not Vibriosis, Katja, it’s still important for you to rehab your main tank while the seahorses are being treated to make sure they have a healthy system to return to. Here is some additional information that will explain how to go about that and that may help you prevent any recurrence of the bacterial infections you’ve been experiencing lately. (I know you’ve probably addressed most all of these issues already, Katja, but I’m going to go over them one by one anyway for the sake of thoroughness. Please bear with me):

Disease-causing (pathogenic) bacteria are opportunistic invaders that are normally present in low numbers but don’t cause problems until the fish is injured, stressed, infested with parasites or otherwise weakened (Indiviglio, 2002). They will then take advantage of the overtaxed seahorse’s impaired immune system and reproduce extremely quickly, causing a variety of illnesses and problems (Basleer, 2000). Some of these are specific to seahorses, such as snout rot and white tail disease, and others are common to all fishes, such as Mycobacteriosis or popeye.

A bacterial infection almost always indicates that there is another problem that is stressing the fishes and weakening their immune response (Indiviglio, 2002). In addition to treating the infection itself, the hobbyist must also identify and correct the underlying problem in order to restore health. Check your water quality and aquarium parameters. A water change and general clean up are usually a good place to start.

One of the best ways to prevent bacterial infections and other disease problems is to provide them with a stress-free environment. Many of the parasites and pathogens that plague our pampered ponies are ubiquitous — present in low numbers in most everyone’s systems or within the seahorse’s body itself (Indiviglio, 2002). As a rule, healthy fish resist such microorganisms easily, and they only become a problem when seahorse’s immune system has been impaired, leaving it susceptible to disease (Indiviglio, 2002). Chronic low-level stress is one of the primary factors that suppresses the immune system and weakens the immune response, opening the way to infection and disease (Indiviglio, 2002). Long-term exposure to stressful conditions is very debilitating. Among other effects, it results in the build up of lactic acid and lowers the pH of the blood, which can have dire consequences for seahorses for reasons we’ll discuss later.

When disease breaks out in an established aquarium it is therefore generally an indication that something is amiss with your aquarium conditions. A gradual decline in water quality is often a precursor of disease (Indiviglio, 2002). Poor water quality is stressful to seahorses. Prolonged stress weakens their immune system. And an impaired immune system leaves the seahorse vulnerable to bacterial, viral, and fungal infections to which healthy, unstressed seahorses are immune. As if that weren’t bad enough, there are a number of environmental diseases that are caused directly by water quality problems.

With this in mind, it’s important to review the most common stressors of captive seahorses. These include the design of the aquarium itself. A poorly designed seahorse setup that lacks adequate cover and shelter, or has too few hitching posts, will be stressful to the occupants (Topps, 1999). Seahorses are shy, secretive animals that rely on camouflage and the ability to conceal themselves for their safety and survival. A sparsely decorated tank that leaves them feeling vulnerable and exposed will be a source of constant stress (Topps, 1999). The seahorse setup should have plenty of secure hiding places so they can conceal themselves from view completely whenever they feel the need for privacy. It should be located in a low traffic area away from external sources of shock and vibration.

Needless to say, rapid fluctuations in temperature, pH, salinity and other aquarium parameters must also be avoided. A large aquarium of 40 gallons or more provides much greater stability in that regard than does a smaller setup. The greater the water volume in the aquarium and sump, the more stable the system will be.

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.

Incompatible tankmates are also stressful for seahorses. This includes not only aggressive, territorial fishes and potential predators but also inoffensive species that are restless, active fishes. Seahorses may be uneasy around fishes that are always on the go, swimming tirelessly back and forth.

Other common stressors for seahorses include overcrowding, overfeeding, stray voltage, and a host of issues related to water quality: ammonia or nitrite spikes, high nitrate levels, inadequate circulation and oxygenation, high CO2 levels and low 02 levels, low pH, etc., etc., etc (Giwojna, Jun. 2002).

In short, if hobbyists provide their seahorses with a stress-free environment, optimum water quality, and a nutritious diet, they will thrive and your aquarium will flourish with a minimum of problems. Preventing disease in the first place is infinitely preferable to trying to treat health problems after the fact. Good seahorse husbandry and diligent maintenance will be rewarded; sooner or later, negligence and poor aquarium management will be punished.

When disease breaks out in an established aquarium it is therefore generally an indication that something is amiss with your aquarium conditions. A gradual decline in water quality is often a precursor of disease (Indiviglio, 2002). Poor water quality is stressful to seahorses. Prolonged stress weakens their immune system. And an impaired immune system leaves the seahorse vulnerable to bacterial, viral, and fungal infections to which healthy, unstressed seahorses are immune.

At the first sign of a health problem:

Because diseases are so often directly related to water quality, or due to stress resulting from a decline in water quality, when trouble arises the first thing you should do is to break out your test kits and check your water chemistry. Very often that will provide a clue to the problem. Make sure the aquarium temperature is within the acceptable range and check for ammonia and/or nitrite spikes first. See if your nitrate levels have risen to harmful levels and look for a drop in pH.

Be sure to check your dissolved oxygen (O2) level too. A significant drop in O2 levels (6 – 7 ppm is optimal) is very stressful yet easily corrected by increasing surface agitation and circulation to promote better oxygenation and gas exchange. At the other extreme, oxygen supersaturation is a red flag indicating a potentially deadly problem with gas embolisms (Gas Bubble Syndrome).

If any of your water quality parameters are off significantly, that may well be the cause of the problem or at least the source of the stress that weakened your seahorses and made them susceptible to disease. And correcting your water chemistry may well nip the problem in the bud, particularly if it is environmental, without the need for any further treatment.

Clean Up & Perform a Water Change

After a quick check of the water chemistry to assess the situation, it’s time to change water and clean up. In most cases, the surest way to improve your water quality and correct the water chemistry is to combine a 25%-50% water change with a thorough aquarium clean up. Siphon around the base of your rockwork and decorations, vacuum the top 1/2 inch of the sand or gravel, rinse or replace your prefilter, and administer a general system cleaning. The idea is to remove any accumulated excess organic material in the sand/gravel bed, top of the filter, or tank that could degrade your water quality, serve as a breeding ground for bacteria or a reservoir for disease, or otherwise be stressing your seahorses. [Note: when cleaning the filter, your goal is to remove excess organic wastes WITHOUT disturbing the balance of the nitrifying bacteria. Do not dismantle the entire filter, overhaul your entire filter system in one fell swoop, or clean your primary filtration system too zealously or you may impair your biological filtration.]

At first glance your aquarium parameters may look great, but there are some water quality issues that are difficult to detect with standard tests, such as a decrease in dissolved 02, transitory ammonia/nitrite spikes following a heavy feeding, pH drift, or the gradual accumulation of detritus. A water change and cleanup is a simple preventative measure that can help defuse those kinds of hidden factors before they become a problem and stress out your seahorses. These simple measures may restore your water quality and correct the source of the stress before your seahorse becomes seriously ill and requires treatment.

In short, strataman, I recommend treating the affected seahorses in a hospital tank with powerful broad-spectrum antibiotics, as explained above. For best results, gradually lower the water temperature in the treatment tank in order to reduce the growth rate and virulence of the bacteria, as previously discussed.

Best of luck getting this infection under control, sir!

Pete Giwojna

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