I’m very sorry to hear that you lost the seahorse that has been having breathing difficulties.
You are correct – if the problem is due to an infestation of external parasites (ectoparasites), then you will need to treat the main tank in order to eliminate the troublesome parasites. Unfortunately, you cannot use formalin or methylene blue for this purpose since those medications will disrupt the beneficial bacteria that provide the aquarium with biological filtration, creating more problems. But there are other options you can consider, as explained below:
In order to treat an infestation of external protozoan parasites, the whole tank must be treated to eliminate the parasites once and for all. There are a number of treatment options that would accomplish that goal without affecting the beneficial nitrifying bacteria that are providing the biological filtration for the aquarium.
For instance, the seahorse tank could be treated with chelated Parinox, praziquantel, quinine sulfate + metronidazole, or possibly Osmotic Shock Therapy (i.e., hyposalinity) after removing any sensitive invertebrates. Let me know if you want to try the hyposalinity, Tammy, a procedure that simply involves lowering the salinity or specific gravity of your aquarium to a level that the parasite cannot tolerate but the seahorses can for a period of several weeks, and which does not require the use of any medication, and I will provide you with detailed instructions for administering it safely. But first I want to discuss the various medications that may be effective in eradicating the protozoan parasites that may be causing respiratory distress. I will list them all below for you:
USE: for ich, Hexamita, costia, ichthyophthirius, ectoparasites, monogenia (trematodes), Hirudinea, parasitic copepods, argulus, Lernaeidae, anchor worms, fish lice, leeches. Also a protozoacide. Antibacterial, antiparasitic — very wide spectrum. Our version of a "cure-all."
DOSAGE: 1/4 teaspoon per 20 gallons of water. Treat once a week for two weeks. If water changes are done, add back the percentage of the medication according to how much of the water was changed.
25 grams for $11.99
Quinine sulfate (Crypto-Pro)
USE: resistant strains of ick (Cryptocaryon irritans), especially on scaleless fish. Protozoans, sliminess of the skin, and ram’s disease (i.e., whirling disease). Also good for resistant strains of Hexamita when combined with metronidazole.
DOSAGE: 1/4 teaspoon per 10 gallons of water. Treat one time and leave in the water for 5-7 days.
For resistant ich in a central system, treat once every three days with a 25% water change before each treatment. Do at least three treatments in a 9-day period.
25 grams for $18.60
USE: same as the quinine sulfate, but packaged for sale to hobbyists and retail aquarists. FDA-approved, child-proof packaging. Bar-coded. Instructions and measuring spoon included.
Metronidazole Powder (Metro-Pro)
USE: anti-protozoan, Hole-in-the-Head disease (Hexamita), Chilodonella (body slime), freshwater ich, Malawi bloat (internal Hexamita), Epistylis in pond fish. (Especially useful for treating intestinal flagellates.)
DOSAGE: 1/4 teaspoon per 20 gallons of water. (50 grams treats approximately 800 gallons.) Treat every 24 hours with a 25% water change between treatments. Treat for 10 days.
To mix in food for internal Hexamita: use 2 teaspoons per pound of food. Use frozen food. Thaw food, mix in powder. Then put the medicated food in a Ziploc bag and lay flat in the freezer until frozen. Feed once a day for 10 days.
25 grams for $14.99
USE: same as the metronidazole, but packaged for sale the hobbyists and retail aquarists. FDA-approved, child-proof packaging. Bar-coded. Instructions and measuring spoon included.
This is a very effective antiparasitic that works equally well against external and internal parasites alike. Like metronidazole, this is a very safe medication that won’t harm the beneficial nitrifying bacteria in your biofilter, so you can use it to treat the main tank.
However, like most antiparasitic medications, invertebrates will not tolerate praziquantel, so be prepared to relocate any snails, decorative shrimp, or microhermit crabs for the duration of the treatments.
Praziquantel can be administered orally via bio-encapsulated feeder shrimp, just like metronidazole, or it can be administered as a series of baths or as a one-time treatment for the main tank. When using it as a bath, the following concentrations are appropriate:
Praziquantel bath at 10ppm for 3 hours or 1ppm for 24 hours.
When treating ectoparasites, it can be added directly to the water in the treatment tank (dose one time and leave in the water for 5-7 days).
You should remove any activated carbon or chemical filtration media during the treatments, of course.
All of the medications I have listed above are safe to use in the main tank, Tammy. They won’t harm the beneficial nitrifying bacteria or affect the biological filtration, but they are all hard on invertebrates so it would be a good idea for you to remove all of the snails and decorative shrimp or starfish (just keep them in a clean, well-aerated plastic bucket of saltwater during the treatment period for safekeeping.)
If you are lucky, you may be able to find one of the medications listed above have a local fish store, but most likely you will have to get them online and have them delivered to you, Tammy. You can obtain all of the medications listed above from National Fish Pharmaceuticals at the following website (just copy the following URL and paste it in your Web browser and it will take you to the right webpage):
National Fish Pharmaceuticals also has a frees free helpline (520-298-7814) that you can telephone for assistance, if necessary.
Best of luck resolving this problem once and for all, Tammy.
Pete Giwojna, Ocean Rider Tech Support