Persistent scratching is not normal and definitely some to be concerned about. It could indicate a potential problem with ectoparasites and I’d be inclined to take steps right now to nip the problem in the bud.
I would recommend giving your seahorses a quick freshwater dip to provide them with quick relief from the ectoparasites that are causing the scratching, followed by treating the entire aquarium with a good antiparasitic medication such as metronidazole, which will not have an adverse effect on the beneficial bacteria that provide biological filtration for the tank.
A freshwater dip is a good place to start with in a case like this, Sir. It’s very safe, most seahorses tolerate it very well, and it may do the trick if you are simply dealing with a light infestation of protozoan parasites. Here’s how to proceed:
A freshwater water dip is simply immersing your seahorse in pure, detoxified freshwater that’s been preadjusted to the same temp and pH as the water the seahorse is accustomed to, for a period of at least 10 minutes. It doesn’t harm them — seahorses typically tolerate freshwater dips exceptionally well and a 10-minute dip should be perfectly safe. Freshwater dips are effective because marine fish tolerate the immersion in freshwater far better than the external parasites they play host to; the change in osmotic pressure kills or incapacitates such microorganisms within 7-8 minutes. A minimum dip, if the fish seems to be doing fine, is therefore 8 minutes. Include some sort of hitching post in the dipping container and shoot for the full 10 minutes with your seahorses.
If you will be using tap water for the freshwater dip, be sure to dechlorinate it beforehand. This can be accomplished usually one of the commercial dechlorinators, which typically include sodium thiosulfate and perhaps a chloramine remover as well, or by aerating the tap water for at least 24 hours to dissipate the chlorine.
If you dechlorinate the dip water with a sodium thiosulfate product, be sure to use an airstone to aerate it for at least one hour before administering the dip. This is because the sodium thiosulfate depletes the water of oxygen and the dip water must therefore be oxygenated before its suitable for your seahorse(s).
However, Sir, freshwater dips alone may not resolve this problem. This is because the ectoparasites are still present in the aquarium and may reinfest the seahorses after they are returned to the main tank following the dip. For this reason, I’d also suggest following up the freshwater dips by administering metronidazole orally, if possible, or by medicating the entire tank with an appropriate regimen of metronidazole.
Metronidazole is ideal for this because of its antiprotozoal properties and is rapidly absorbed from the GI tract, has anti-inflammatory effects, and was designed specifically to treat protozoal infections by disrupting their DNA.
If the seahorses are still eating, administering the metronidazole orally via gut-loaded shrimp is often extremely effective. This is accomplished exactly the same way as with other antibiotics. Start by dissolving roughly 50 mg (about 1/4 of a 250 mg tablet is good) of metronidazole into a tablespoon of hot water. Then soak commercial flake food in the tablespoon so that the medication is absorbed into the food, and feed the medicated flakes to small live ghost shrimp. When the shrimp’s guts are loaded with the medicated flakes (you will be able to see the color of the flake food in their distended guts), feed the gut-loaded shrimp to the ailing seahorse. Keep the seahorse on a strict diet of live shrimp gut-loaded with Metronidazole for 5-10 days.
Use the medicated flakes to gut load only as many shrimp as the affected seahorse can eat in one day. Each day you’ll have to prepare new metronidazole-soaked flakes and gut load a day’s worth of new ghost shrimp. Keeping the seahorse on a strict diet of live shrimp gut-loaded with metronidazole for 5-10 days will help eliminate persistent parasites.
As an alternative to gut loading or bioencapsulation of the medication, the resulting metronidazole solution can also be injected into freshly killed ghost shrimp or even frozen mysids using a fine syringe and then administered by target feeding the ailing seahorse with the injected shrimp. Again, you’ll have to prepare new metronidazole solution daily and inject enough of the frozen shrimp for a day’s worth of feedings.
Your local fish store should carry a medication designed for aquarium use whose primary ingredient is metronidazole (e.g., Seachem Metronidazole, Flagyl, Metro-MS by FishVet, Hexamit, etc.). Just follow the instructions on the package and be sure to use the marine dose. Temporarily relocate sensitive invertebrates such as decorative shrimp until after the treatment regimen has been completed.
Okay, that’s the rundown on treating intestinal flagellates with metronidazole in order to correct the loss of appetite, Sir. I prefer to administered orally whenever possible, but if that’s not feasible for you, you can also add it directly to the aquarium water.
Seachem Metronidazole Aquarium Fish Medication – 100 g
Parasitic and Bacterial infections don’t stand a chance with Metronidazole. When you find your fish infected with such nasty bugs as Ich or Hexamita, grab the Metronidazole and say goodbye to infection. This fast and effective treatment is safe for biological filtration and is easily removed with carbon after treatment. For freshwater or marine fish.
PACKAGE SIZE 100 GRAM
TREATS UP TO 265 TO 530 GALLONS
TYPE OF DISEASE BACTERIA, PARASITE
AQUARIUM TYPE FRESHWATER, SALTWATER
ACTIVE INGREDIENTS METRONIDAZOLE
INVERT SAFE WITH CAUTION
Do not use UV, ozone or chemical filtration during use.
Use 1-2 measures (each about 100 mg each) for each 10 gallons. Measurer included. Repeat every 2 days until symptoms disappear.
To feed, blend 1 measure with about 1 tablespoon of frozen food paste.
Best of luck resolving this problem and restring your seahorses to normal again, Sir.