I’m very sorry to hear about the problems you’ve been having with your herd lately.
Yes, it is quite possible to cure bacterial infections in seahorses once the infection has progressed to the stage where localized loss of coloration occurs. The measures you have taken should help. Neomycin sulfate is a very good antibiotic for seahorses and a 25% water change to improve water quality was an excellent first aid measures to take.
Increasing the dosage of the neomycin sulfate is very appropriate. When administering antibiotics, the proper dosage for a marine aquarium is usually at least twice the recommended dosage for freshwater. In the case of neomycin, some seahorse keepers increase the dosage of neomycin sulfate up to four times the recommended dosage for saltwater tanks, or eight times the suggested dosage for freshwater (Keith Gentry et al.).
For best results, consider combining the neomycin sulfate with other compatible antibiotics. For example, treating with neomycin in conjunction with nifurpirinol (the active ingredient in Furanase) and/or kanamycin creates a synergistic combination of antibacterials that is much more potent than any of these excellent antibiotics used alone, as discussed below:
This is a potent broad-spectrum, gram+/gram- 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 to further increase its efficacy. Like other gram-negative antibiotics, it will destroy your biofiltration and should be used in a hospital tank only.
Nifurpirinol is a nitrofuran antibiotic that is the active ingredient in many commercial preparations designed for use in the aquarium. It is stable in saltwater and rapidly absorbed by fish, making it the preferred treatment for fungal infections in seahorses (Burns, 2002). Nifurpirinol is photosensitive and may be inactivated in bright light, so use this medication only in a darkened hospital tank.
Nifurpirinol may be combined with neomycin (see below) to produce a potent broad-spectrum medication that’s effective against both fungus and bacteria. Nifurpirinol/neomycin is therefore a great combination to use when you’re not certain whether the infection you are treating is fungal or bacterial in nature.
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.
Antibiotics are often most effective when they’re ingested, so the prospects for full recovery are better when the treatment is begun while the seahorse is still eating and the medications can be administered orally via bio-encapsulated feeder shrimp. The next best thing to ingesting the antibiotics is upping the dosage of the medications you add to the hospital tank, which you have already done. The prognosis is poor once the bacterial infection has advanced to the point that tissue erosion occurs in the discolored areas become open ulcers or bloody lesions, and your seahorse has not reached that point, so don’t give up hope, Helen.
My recommendation would be to add nifurpirinol (i.e., Furanase) and/or kanamycin to your treatment regimen along with the neomycin sulfate, and then to decrease the temperature in your hospital tank as much as possible. Reducing the water temperature and cooling down the microbes will slow down their metabolism and rate of reproduction accordingly, and give the seahorse’s immune system a better chance to fight off the disease (Giwojna, Oct. 2003).
A simple way to drop the water temp in your hospital tank is to position a small fan so it blows across the surface of the water continually (Giwojna, Oct. 2003). This will lower the water temperature a few degrees via evaporative cooling (just be sure to top off the tank regularly to replace the water lost to evaporation). Leaving the light off on your hospital tank in conjunction with evaporative cooling can make a big difference and help you knock out this tail infection (Giwojna, Oct. 2003). Tropical seahorses will be fine as low as 68 F providing you drop the aquarium temperature gradually. Most likely you won’t be able to drop the temperature that far without a chiller, but just lowering the temperature a few degrees can make a big difference when fighting bacterial infections.
If you refer to an earlier post on the Ocean Rider Club on Yahoo under the heading "Re: Sick seahorse — please help!" there is a good discussion of the sort of factors that are often associated with such bacterial infections and disease problems in general, as well as some of the measures you can take to help prevent them in the future. You can find it at the following link:
Click here: OceanRider : Message: Re: Sick seahorse-please help! http://groups.yahoo.com/group/OceanRider/message/9573
That detailed discussion goes over several things you can do short of breaking down your aquarium and starting over that can help keep this infection from spreading and also prevent the recurring problems with Gas Bubble Syndrome you have been having, so please route read through a carefully.
Best of luck treating your ailing seahorse, Helen. By the way, congratulations on your fourth-generation juveniles! Closing the life cycle with seahorses is quite an accomplishment, and maintaining your homegrown seahorses through several successive generations is all the more so. Hopefully, those preventative measures covered in the link I posted above will assure that your juveniles are not affected.