Pete Giwojna

Dear Sandy:

I’m very sorry to hear about the problems your seahorses have developed. The loss of coloration and resulting white, blotchy patches can result from bacterial infections that attack the skin, especially White Patch Disease (Myxobacteria) or ciliate protozoan parasites that attack the skin (e.g., Uronema). Both of these are serious conditions that can be fatal if they are not treated promptly. (Has your seahorse tank been running warmer than normal lately, Sandy? Heat stress and/or temperature spikes during a summertime heat wave are often associated with these types of problems.)

I will provide you with information about both of these diseases below, but it often proves impossible for hobbyists to distinguish between the two problems without laboratory tests, since the initial symptoms are pretty much the same.

I would therefore suggest a treatment regimen that can be effective against both bacterial skin infections such as White Patch Disease and ciliated parasites such as Uronema. This can be accomplished by treating the seahorses with antibiotic therapy in isolation, reducing the water temperature as much as possible, and administering a series of formalin baths while the seahorses are being treated in your hospital tank.

White Patch Disease or Marine Columnaris is typically caused by Myxobacteria. A white, slimy coating on the body is very characteristic of this condition. It is sometimes referred to as "bacterial fungus," and indeed Myxobacteria infections are often confused with fungus although they are caused by gram-positive bacteria. Here is some information about this affliction from my new book on seahorses (Complete Guide to the Greater Seahorses in the Aquarium, TFH Publications, unpublished):

<Open quote>

Marine columnaris is a highly contagious disease caused by a Myxobacterium (Flexibacter sp.) that corresponds to the columnaris infections so commonly seen in freshwater fish (Basleer, 2000). The bacterium Flexibacter is a long, slender rod-shaped organism (0.5- 1.0 microns in diameter, and some 4-10 microns long) that is easily identified under the microscope by its characteristic gliding motion (Dixon, 1999). They are unusually mobile bacteria. They are very active when observed microscopically, gliding rapidly across the viewing field (Dixon, 1999). This family of bacteria (Cytophaga or Myxobacteria) causes a condition commonly known as columnaris because of their tendency to stack up in columns (Prescott, 2001b). When large numbers of the bacteria pile up, they form distinctive haystacks several layers thick where the infection is heaviest (Dixon, 1999).

These bacteria are typically associated with stress, and columnaris is very often associated with a sudden rise in temperature. It is frequently seen in temperate seahorses suffering from heat stress or among tropical seahorses that have been subjected to a temperature spike during a summertime heat wave (Giwojna, Nov. 2003).

This is primarily an epithelial disease that often presents as a grayish white film that spreads over the fish’s skin, particularly on the head region (Giwojna, Nov. 2003). The whitish plaques spread by radial expansion and may penetrate into deeper tissues, becoming yellow or orange due to masses of pigmented bacteria that stack up in columns forming the haystacks that are characteristic of the condition (Basleer, 2000).

Columnaris is often described as a milky, slime-like film that can be observed with the naked eye (Giwojna, Nov. 2003). The bacteria are actually pale yellow, and the whitish skin lesions may become yellowish or even orange as the bacteria pile up (Prescott, 2001b). Depending on how many layers of Myxobacteria are stacked up in any given area, this gives the fish a patchy white to yellowish appearance (Giwojna, Nov. 2003). These bacteria produce enzymes that can dissolve the skin and decay the underlying musculature.

Hobbyists most often refer to marine columnaris as White Patch Disease and it is often mistaken for a fungal infection (Giwojna, Nov. 2003). Although the head and eyes are most often infected, the slimy white patches can appear anywhere on the body and, in seahorses, the tail is also often affected.

Columnaris infections vary greatly in virulence depending on the strain involved and the conditions that contribute to the disease (most notably water temperature), and the symptoms of the disease can vary accordingly (Giwojna, Nov. 2003). There is an acute form of the disease that may kill very quickly when the head is involved, often within 24 hours of the first symptoms.

Less virulent forms of columnaris allow time for the symptoms to be recognized and treated. For example, milder strains may produce localized shallow ulcers where the white patches first appeared that respond very well to prompt treatment with the proper antibiotics (Giwojna, Nov. 2003). The gills are another common site of infection and are sometimes the only affected area. Respiratory distress may be the only symptom in such cases, and if the gills are examined, excessive amounts of mucous are to be expected (Giwojna, Nov. 2003). Damage to the gills from these bacteria is evident as brownish dead patches of tissue that are often attacked by secondary fungal infections (i.e., Saprolegnia; Prescott, 2001b). Cases of columnaris involving the gills typically respond favorably to nifurpirinol (Giwojna, Nov. 2003).

Affected fish will become very listless and lethargic in the later stages, with reduced eye movement in seahorses (Giwojna, Nov. 2003). Reluctance to feed is very typical and the fish will often exhibit labored breathing due to the involvement of the gills (Prescott, 2001b).

If caught early and treated promptly, antibacterial compounds are often effective, especially when accompanied by a decrease in water temperature. Some of the effective medications for treating columnaris include oxytetracycline (administered orally) and especially combination sulfa drugs that include trimethoprim or neomycin combined with various sulfa compounds (Giwojna, Nov. 2003).

Columnaris is often associated with temperatures that are elevated beyond what is normal, or exposure to a sudden rise in temperature, and both the mortality and acuteness of the disease will increase at higher water temperatures (Giwojna, Nov. 2003). As with other bacterial infections, stress plays a critical role in the initiation of columnaris disease. Aside from heat stress, other risk factors for columnaris include physical injury, low dissolved oxygen levels, crowding, organic pollution, parasites, and high nitrite levels (Prescott, 2001b).

At the first sign of White Patch Disease or Marine Columnaris, I recommend treating the affecting seahorse(s) immediately in a hospital tank using neomycin together with sulfa compounds (Giwojna, Nov. 2003). Drop the temperature in the hospital tank during the course of the treatments. Reducing the water temperature will slow the metabolism and reproductive rate of bacteria in general, making them easier to control, and the virulence of columnaris, in particular, is markedly reduced at lower temperatures (Giwojna, Nov. 2003).

As with marine ulcer disease, there are a number of parasitic infections that can easily be mistaken for columnaris. Brooklynella, Costia and Uronema parasites all cause cloudiness or turbidity of the skin accompanied by heavy mucous production in their initial stages, which are similar to the white patches and filmy appearance of a columnaris infection (Giwojna, Nov. 2003). In their later stages, these parasitic infections result in respiratory distress and ulcers or open sores that are very like the symptoms of columnaris when the enzymes the bacteria produce erode away the skin and the gills are involved (Giwojna, Nov. 2003). Parasitic infections are often followed by secondary bacterial/fungal infections, and such parasites are one of the stressors that can result in a columnaris infection. This can make it difficult to determine whether you are dealing with columnaris, a parasite problem, or a mixed infection (Giwojna, Nov. 2003).

For that reason, I recommend that you treat for parasites at the same time you are administering neomycin and nifurpirinol to combat columnaris. In other words, combine your antibiotic therapy with hyposalinity in the hospital tank (lower the specific gravity to 1.011), or with daily applications of merbromin, or medication with metronidazole, or all of the above, as explained for treating marine ulcer disease (Giwojna, Nov. 2003).

Once it’s established in the aquarium, columnaris is highly communicable, as are parasitic infections, and it is very advisable to clean up and sterilize the main tank as best you can while the affected seahorses are undergoing treatment in the hospital ward (Giwojna, Nov. 2003). Combine a 25%-50% water change in your main tank with a thorough system cleaning as previously described (Giwojna, Nov. 2003). <End quote.>

Since we have no way of telling which type of skin infection (bacterial or protozoal) your seahorses have at this time, here is some additional information on Uronema from my new book that discusses Uronema marinum, the most common of the protozoan parasites that attacks the skin in seahorses, including the most useful treatment options:

<Open quote>
Uronema marinum

Uronema marinum is the marine equivalent of the Tetrahymena pyriformis parasites that plague freshwater fish (Basleer, 2000). Uronematids are probably the most commonly encountered protozoan parasites of seahorses in the aquarium. They frequently plague wild-caught seahorses and store-bought fish in particular. Unfortunately, they are also one of the deadliest and difficult to eradicate marine parasites.

They live in seawater and normally feed on bacteria and dead skin, but they are opportunistic invaders that are always on the lookout for food, and are quick to take advantage of weakened fish (Kollman, 2003). It is when conditions favor them and their numbers get out of hand that Uronema becomes a problem. Under those circumstances, they soon begin to attack healthy tissue as well as dead material, invading the gills and muscles, eating red blood cells, and infiltrating the internal organs (Kollman, 2003).

High temperatures and poor water quality are among the environmental factors that favor Uronema. Elevated water temps speed up their life cycle and accelerate the growth rate of Uronematids accordingly (Kollman, 2003).

These ciliated parasites are very common on freshly imported wild fishes suffering from shipping stress (Basleer, 2000). Long-distance shipping is one of the factors that commonly contributes to Uronema problems. The deteriorating water quality in the shipping bags of fish transported for 24-48 hours is very conducive to their growth. Low pH, too much ammonia and organic waste, too little dissolved oxygen, and the presence of weakened fish with compromised immune systems all combine to create ideal conditions for these parasites (Basleer, 2000). They feed on damaged tissue, multiply quickly, and invade healthy tissue as their population explodes (Basleer, 2000).

The initial symptoms are excess mucus production, heavy breathing, and loss of color (Basleer, 2000). As the disease progresses, pale patches or bloody sites appear, which become large ulcer-like wounds as the Uronema parasites multiply rapidly and invade the underlying muscle tissue in the advanced stages (Basleer, 2000). Infected fish often scratch these irritated areas. These open bloody lesions are often mistaken for bacterial infections (e.g., marine ulcer disease or "flesh-eating bacteria"), and the affected fish are doomed if antibiotic therapy is administered on the basis of such a misdiagnosis.

These dreaded parasites also infect the gills, and as with Brooklynella, heavy gill infections may result in dead by suffocation before the characteristic skin lesions develop (Basleer, 2000). When skin lesion do appear, the open wounds invite secondary bacterial infections, which further complicate the clinical picture.

Microscopic examination of skin smears can confirm the diagnosis of Uronema. Under the microscope, Uronema marinum parasites appear as pear-shaped, single-celled ciliates with a single large macronucleus and long hairlike cilia at the rear end (Kollman, 2003). Numerous small (35-50 microns), fast-moving, oval or pear-shaped parasites will appear on skin and fin smears (Basleer, 2000).

Formalin, malachite green, or formaldehyde/malachite green combination drugs are effective treatments (Basleer, 2000). The treatment needs to be maintained for at least 21 days to cover the life cycle of the parasites. Chloroquine phosphate, quinine hydrochloride and quinacrine hydrochloride (antimalarial drugs) also work well but are difficult to obtain, difficult to use, and difficult to dispose of properly (Kollman, 2003).

Freshwater baths, concentrated baths in methylene blue, and hypersaline baths at 45-50 ppt are also very helpful. Even 10-second dips in a 3% hydrogen peroxide solution are known to be effective. The peroxide dipping solution is prepared by taking one gallon of dechlorinated freshwater and then removing 10-oz of the water and replacing it with 10-oz of 35% hydrogen peroxide instead. This formula will produce a 3% solution of hydrogen peroxide for the brief dip (Kollman, 2003).

In addition, Thom Demas, the Senior Aquarist at the Tennessee Aquarium, reports that raising the salinity of the system to 38-40 ppt while gradually lowering the temperature will greatly slow down the growth rate of Uronema and make it much easier to control (Demas, pers. com.). Uronema doesn’t seem to respond to hyposalinity and I also feel that hypersalinity produces better results for this parasite. It appears that Uronematids are unique among ectoparasites in their tolerance for hyposalinity, so treat accordingly. They cannot withstand freshwater, but hyposalinity seems to be quite another matter.

With all these different treatment options for Uronema, one would think that these parasites would be fairly easy to control. Nothing could be further from the truth! Uronema is a very stubborn pest and terribly difficult to eradicate from your system once and for all. The problem is that formalin, malachite green, and the various dips and baths all do a fine job of killing the Uronema ectoparasites that are on the skin and gills of the fish, but they cannot touch the parasites that have penetrated within the fish’s body. The parasites that are attacking the muscle tissue, internal organs, and red blood cells aren’t touched by such methods and they are the ones that do the irreparable damage. What is needed is therefore a way to get the antiparasitics inside the affected fish where they can kill the ciliates that have invaded the tissue.

Dr. Alistair Dove, the Aquatic Pathologist at the New York Aquarium, has found the solution. He reports that intramuscular injections of metronidazole at a dosage of 50mg/kg repeated every 72 hours for a total of 3 treatments work extremely well for eliminating Uronema in seahorses (Al Dove, pers. com.). The IM injections deliver the drug inside the seahorse’s body, precisely where it’s needed most. Of course, we humble hobbyists cannot manage such injections, but we sure can bioencapsulate metronidazole by gut-loading live shrimp with it and get the medication into our seahorses that way. That will allow us to attack the parasites from the inside and the outside at the same time.

Because Uronema is so difficult to control, Basleer recommends treating it with a combination of treatments. He suggests treating the main tank with formalin/malachite green and then adding daily baths in freshwater and concentrated methylene blue for best results (Basleer, 2000).

Lower the water temperature during the treatment period and stay on top of the water quality in your hospital tank. Make partial water changes as necessary to keep your aquarium parameters perfect. <End quote>

That sums up the most likely causes for those blotchy, white patches that have appeared on your seahorses, Sandy. I recommend you treat your H. erectus with a combination of antibiotics, reduce the water temperature to as low as 68°F if possible, and administer a series of formalin baths (see instructions below) every other day for total of at least three treatments.

The antibiotics I suggest for this are either neomycin sulfate or kanamycin sulfate (both aminoglycoside antibiotics) combined with TMP-sulfathiozole sodium.

Formalin baths used in conjunction with these antibiotics will help eliminate any ectoparasites or secondary fungal infections that may be involved. Formalin is basically a 37% solution of formaldehyde and water. It is a potent external fungicide, external protozoacide, and antiparasitic, and seahorse keepers commonly use formalin to cleanse new arrivals of ectoparasites during quarantine. Formalin (HCHO) is thus an effective medication for eradicating external parasites, treating fungal lesions, and reducing the swelling from such infections. As such, formalin baths combined with the antibiotics recommended above can be highly effective in treating White Patch Disease or Marine Columnaris when treatment is begun during the early stages.

Many commercial formalin products are readily available to hobbyists, such as Kordon’s Formalin 3, Formalin-F sold by Natchez Animal Supply, and Paracide-F, sold by Argent Chemical Laboratories. Or whatever brand of formalin is available at your fish store should work fine, Elina.

A formalin bath simply involves immersing the seahorse in a container of saltwater which contains the proper dosage of formalin for a period of 30-60 minutes before transferring it to your hospital tank. Include a hitching post of some sort in the container and follow these instructions: place the fish in a three-gallon bucket or a similar clean, inert container containing precisely one gallon of siphoned, aerated tank water. Medicate the bucket of water with with the appropriate amount of formalin for a concentrated bath according to the directions on the label. Place an airstone in the bucket and leave the fish in the bath for 30-60 minutes. If at any time the fish becomes listless, exhausted or loses its balance, immediately place the fish in clean, untreated water in your hospital tank.

I want you to be aware of these precautions when administering the formalin bath:
Formalin has limited shelf life and degrades to the highly toxic substance paraformaldehyde (identified as a white precipitate on the bottom of the solution); avoid using any formalin product which has such a precipitate at the bottom of the bottle.
Formalin basically consumes oxygen so vigorous aeration must be provided during treatment.

Time the bath closely and never exceed one hour of chemical exposure at this concentration.

Observe the seahorse closely during the bath at all times, and it show signs of distress before the allotted time has elapsed, remove it from the treatment immediately.

If you can obtain Formalin 3 from Kordon at your LFS, Elina, these are the instructions you should follow for your formalin dip:

(a) To a clean, non-metallic container (i.e., a plastic bucket), add one or more gallons of fresh tap water treated with Kordon’s AmQuel . For marine fish use freshly prepared saltwater adjusted to the same specific gravity (or salinity) as in the original tank. Make sure the temperature in the container is identical to that in the aquarium
(b) Add 1 teaspoons of Formalin·3. This produces a concentration of 100 ppm. formaldehyde.
(c) Agitate the solution with an airstone and adjust for a moderately strong flow of air.
(d) Remove the fishes to be treated and deposit them in the container for a treatment period of not more than 50 minutes. Immediately after the treatment period, or if signs of distress are noted, remove the fishes to a previously prepared recovery tank. The fishes may be returned to their original tank, but the presence of the original disease-causing agents in the tank water may result in a reoccurrence of the disease condition.
(e) Observe recovering fishes. Make sure that tankmates do not molest them during recovery.
(f) Repeat treatment as needed, every week. Each treatment is very stressful to the treated fishes. Do not reuse the dip solution.

For additional information on treating fishes with Formalin 3 by Kordon, see the following web page:

Click here: KPD-54 Formalin-3

If you get another brand of formalin, just follow the instructions that it comes with for a concentrated bath or dip (not prolonged immersion or a long-term bath).

Here is some additional information on the antibiotics that should produce the best results
for these conditions:


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.

neomycin sulfate

Neomycin is a very potent gram-negative aminoglycoside 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, nifurpirinol or sulfa compounds 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.

Sulfathiazole Sodium

This is a wide spectrum antibiotic that is also helpful in controlling protozoa. It uses sulfur as a keratolytic agent, promoting sloughing of dead skin cells and excess mucous production to assist fish in shedding parasites and pathogens. It is the most soluble of all the sulfa drugs and may be combined with neomycin to produce a more effective broad-spectrum antibiotic with potent synergistic effects.

Trimethoprim and Sulfathiazole Sodium (TMP-Sulfa)

A potent combination of medications that’s effective in treating both gram-positive and gram-negative bacterial infections. It exerts its anti-microbial effect by blocking two consecutive steps in the biosynthesis of nucleic acids and proteins essential to many bacteria, making it very difficult for bacteria to develop resistance to the medications. TMP-Sulfa may be combined with other sulfa compounds to further increase its efficacy and decrease the chance of resistant strains developing.

TMP-Sulfa will knock your biofilter for a loop, so be sure to use it in the hospital tank only.

You can get all of these antibiotics online from National Fish Pharmaceuticals at the following URL:

Click here: Fish Medications

You may also be able to find medications containing these antibiotics as their active ingredient from a well stocked fish store.

One simple way a simple way to drop the water temp in your hospital tank to position one or more small fans so they blows across the surface of the water continually (Giwojna, Oct. 2003). This will lower the water temperature a several degrees via evaporative cooling (just be sure to top off the tank regularly to replace the water lost to evaporation). Leaving the cover/hood and light off on your seahorse tank in conjunction with evaporative cooling can make a surprising difference, and just lowering the water temperature a few degrees can help a lot when controlling protozoan parasites or bacterial infections.

In a pinch, some hobbyists will even freeze plastic bottles 3/4 full of water and float the frozen bottles of water in their tank during the hottest part of the day. If necessary, that may worth trying in your case too, depending on how well your water temp responds to the other measures.

As long as either of the seahorses will feed, target feed them with Vibrance-enriched frozen Mysis to encourage them to eat. The Vibrance includes beta-glucan as an active ingredient, and the beta-glucan is a potent immunostimulant that will boost their immune systems and help them fight off disease.

Antibiotic therapy combined with reduced water temperature and a series of formalin baths is your best bet for getting this problem under control, Sandy. Here’s hoping your seahorses respond well to treatment and are soon feeling much better.

Pete Giwojna

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