I’m very sorry to hear about the problem your seahorses have developed. The cloudy eye and sloughing of the skin suggests you are dealing with a bacterial infection, most likely marine ulcer disease, which can be considered a form of skin rot. Here is some information on marine ulcer disease excerpted from my new book, which may help you decide if that’s what you’re dealing with or not::
MARINE ULCER DISEASE, 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 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 and neomycin, oxytetracycline(orally), nifurpirinol, sulfonamide and other sulfa compounds, or streptomycin. 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).
Tetracycline or oxytetracycline can also be administered in the same ways. Use it at a dosage of 100 mg/liter of water for a 24-hour bath or 1 gram/100 liters for prolonged immersion (i.e., a 4-day bath), Prescott, 2001c.
All things considered, I would say that chloramphenicol (i.e. Chloromycetin) is the treatment of choice for marine ulcer disease and most Vibrio infections. It is effective both as a bath for prolonged immersion or when administered orally. If the seahorses are no longer eating, then administering the chloramphenicol to the treatment tank becomes the only option.
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 i or neomycin nstead. A fish medication that includes kanamycin sulfate or neomycin sulfate as its primary ingredient should be available from any well-stocked LFS:
Kanamycin & neomycin sulfate
These are potent broad-spectrum, gram+/gram- aminogylcoside antibiotics. They are 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 or sulfa compounds (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, I would suggest combining the kanamycin or neomycin with triple sulfa to create an even more effective combination of medications with a synergistic effect. Treatment should be carried out in a hospital tank and the water temperature in the treatment tank should be gradually lowered. If possible, reduce the water temperature to 66-68°F.
If, for some reason, you have difficulty locating the kanamycin, 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 seahorses seahorses, 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.)
Best of luck treating your ailing seahorses, Nancy.