parasites in nursery

Dear Seagazer:

I have seen older seahorse fry and juveniles scratching when they were being stung by hydroids, especially the mobile Medusa stage — those tiny micro-jellyfish that look like silvery bubbles and swim with a herky-jerky motion. If you have live rock and live sand in your nursery tank, hydroids infestation is a strong possibility, since those are ideal conditions for hydrozoans. Examine your nursery tank carefully for any signs of the dreaded ‘droids or the transparent medusae. Here’s what to look for:

If you rear seahorse fry for any length of time, sooner or later you will have to deal with an infestation of hydroids in your nursery tank(s). Hydrozoans are colonial stinging animals that are the scourge of the seahorse breeder because they can take over a nursery almost overnight and wreak havoc on the fry. The typical hydroid colony has a stem with a variable number of polyps growing on it, and each of these polyps bears numerous tentacles that are liberally studded with knobby nematocysts (batteries of deadly stinging cells). There are many different kinds of hydroids and they appear in the aquarium in many different guises: many colonies are stalked; some have fingerlike projections, others look like tiny pink fuzzy balls or appear like cobwebs (the webbing kind usually spread along the bottom or grow on the aquarium glass along the substrate).

Even a large hydroid colony appears harmless to the naked eye. It takes a much closer look to reveal the dreaded ‘droid’s lethal nature, as described in The Complete Guide to Dwarf Seahorses in the Aquarium by Alisa Wagner Abbott:

"Studying the colony under high magnification, one soon becomes lost in an extraordinarily complex, living world–a microcosm in which a beautiful but deadly ballet is conducted on a microscopic scale (Rudloe, 1971). Hungry polyps, some resembling snapdragons, others looking more like daisies or tulips, expand their knobby, translucent tentacles, slowly flexing and languidly waving them about, lulling the observer with their slow-motion ballet — until they abruptly and quite unexpectedly snap up a bit of planktonic life, stinging it, drawing it in with one violent contraction, digesting it, and then re-expanding like a blossoming flower to hunt again (Rudloe, 1971). There are many such polyps in a colony, hundreds of them, each of which is armed with many tentacles and countless nematocysts, and at any given moment, some of them will be dormant and still, some will be expanded and lazily casting about for prey (Rudloe, 1971), and still others actively feeding (Abbott, 2003)."

Hydroids are insidious because they start out so small and insignificant, yet spread so quickly. Many species can spread asexually by fragmentation as a microscopic speck of the parent colony. All of the troublesome types have a mobile hydromedusae stage, which look like miniscule micro-jellyfish, and can spread sexually in this way as well (Rudloe, 1971). The mobile medusae swim about with a herky-jerky, pulsating motion and are often mistaken for tiny bubbles due to their silvery, transparent, hemispherical bodies (Rudloe, 1977). These tiny jellies often go unrecognized until they begin to settle and are discovered adhering to the tank walls. They will have a large "dot" in the middle of their bodies and smaller ones at the base of their nematocysts (Abbott, 2003). Both the polyp stage and the medusa stage sting (Rudloe, 1977) and are capable of killing or injuring seahorse fry. Multiple stings can kill the babies outright, but they are often only injured by the nematocysts, which damage their integument and leave them vulnerable to secondary infections. Many times it is a secondary bacterial or fungal infection that sets in at the site of the injury which kills the fry.

In your case, Seagazer, your juveniles are both enough now that a hydroid sting would be more of the irritation that of fatal injury. But multiple stings certainly would be a serious source of stress and there’s always that danger of secondary infections.

If you feel an outbreak of hydroids could be responsible for the scratching, Seagazer, they can easily be eradicated from your nursery tank using fenbendazole (brand-name Panacur). Just let me know if you think hydroids are the culprits and I will provide you with complete instructions for eliminating them with fenbendazole.

If your tank is free of hydroids, then it’s very likely to be a parasite problem of some sorts, just as you suspect. It could be ectoparasites that attack the skin and gills (Uronema, Cryptocaryon, Amyloodinium, Costia, Cryptobia, etc.), or nematodes, or — well, or a whole lot of things. Doesn’t really matter. There are number of treatment options you can choose from that are effective against all those parasites.

For example, you could treat your itchy juveniles with a series of freshwater dips and/or concentrated dips in methylene blue and/or formalin baths. Any or all of those should safely provide your 1-2 month old youngsters with some immediate relief.

One option would be to administer a daily freshwater dip to your juvies until the scratching stops, as discussed below:

Freshwater Dips

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 (Giwojna, Dec. 2003). 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 (Giwojna, Dec. 2003). 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 (Giwojna, Dec. 2003).

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 (Giwojna, Dec. 2003).

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).

Observe the horse closely during the dip. You may see some immediate signs of distress or shock. Sometimes the horse will immediately lie on its side on the bottom. That’s a fairly common reaction — normal and to be expected, rather than a cause for concern, so don’t be alarmed if this happens. Just nudge or tap the seahorse gently gently with your finger if it lies down on its side. Normally, the seahorse will respond to the slight nudge by righting itself again and calm down for the duration of the dip. However, if it does not respond, stop the treatment.

Most seahorses tolerate the treatment well and experienced no problems, but if you see continued signs of distress — twitching, thrashing around etc. — stop the treatment.

After you have completed the dip and returned the seahorses to the aquarium, save the dip water and examined it closely for any sign of parasites. The change in osmotic pressure from saltwater to freshwater will cause ectoparasites to lyse (i.e., swell and burst) or drop off their host after 7-10 minutes, and they will be left behind in the dipping water. Protozoan parasites are microscopic and won’t be visible to the naked eye, but some of the other ectoparasites can be clearly seen. For example, monogenetic trematodes will appear as opaque sesame seeds drifting in the water (Giwojna, Aug. 2003) and nematodes may be visible as tiny hairlike worms 1/16-3/16 of an inch long. Other parasites may appear as tiny dots in the water. Freshwater dips can thus often provide affected seahorses with some immediate relief by ridding them of these irritating pests and can also aid their breathing by flushing out gill parasites.

For best results, consider following up the 10-minute freshwater dip with a very brief (5-10 seconds — no more than 10 seconds maximum) dip in a solution of methylene blue between 30-50 ppm, as described below. Prepare the solution of methylene blue using saltwater from your seahorses tank ahead of time, before you do the freshwater dip, so you can dip them in the meth blue for 5-10 seconds right after you do the freshwater dip. Time the very short Methylene blue dip closely — maybe keep each seahorse in your hand while you dip it in the blue so there’s no fumbling around to capture it when time’s up — pull the pony out after 5-10 seconds and immediately return it to the main tank afterwards.

If you can obtain the Kordon brand of Methylene Blue (available at most well-stocked local fish stores), their suggested treatment protocol for treating external parasites as a dip is as follows:

For use as a dip for treatment of external parasitic protozoans:

(a) Prepare a nonmetallic container of sufficient size to contain the fish to be treated by adding water similar to the original aquarium.
(b) Add 5 teaspoons (24.65 ml) per 3 gallons of water. This produces a concentration of 50 ppm. It is not recommended that the concentration be increased beyond 50 ppm.
(c) Place fishes to be treated in this solution for no longer than 10 seconds.
(d) Return fish to original aquarium.

See the following link for more information on treating with Kordon’s Methylene Blue:

Click here: KPD-28 Methylene Blue
http://www.novalek.com/kpd28.htm

If your methylene blue is not Kordon (KPD-28) Methylene Blue, Michelle, then disregard the instructions above and follow the manufacturer’s instructions for using your brand as a bath or dip instead.

Another alternative would be to use formalin treatments at 1ml/gal for a 1 hour bath
every other day until the scratching stops for up to 3 treatments. If you try the formalin baths, be sure to observe the precautions outlined below:

Formalin Baths

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, Pam.

A formalin bath simply involves immersing the seahorse in a container of saltwater which contains the proper dosage of formalin for a period of 60 minutes before returning it to the main 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 up to 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, Pam, these of the instructions you should follow for your formalin dip:

METHOD 2 (DIP) FOR THE PREVENTION OR TREATMENT OF FISH DISEASES

(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, she the following web page:

Click here: KPD-54 Formalin-3
http://www.novalek.com/kpd54.htm

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).

Any of the dips are baths mentioned above should provide your itchy youngsters with immediate relief, Seagazer. However, for a heavy infestation, it is also necessary to treat the nursery tank in order to eradicate the parasites. There are run number of treatment options that would accomplish that goal.

For instance, the nursery tank could be treated with chelated copper sulfate, Parinox, Osmotic Shock Therapy (i.e., hyposalinity), or possibly metronidazole. As long as your nursery tank doesn’t house in the delicate invertebrates, any of those treatments could clear up the parasites. I would try copper sulfate, Parinox or OST before I resorted to the metronidazole, however.

Which of these treatment options is best for you, Seagazer, will likely depend on what medications you have on hand or that are readily available in your area. If your tank is free of hydroids and you suspect the scratching is due to parasites, just let me know if you would like to try one of these treatments on your main tank and I’ll be happy to provide you with complete instructions for that form of therapy.

Best of luck with your itchy seahorse fry, Seagazer! Here’s hoping the scratching is soon a thing of the past.

Respectfully,
Pete Giwojna

Dear Seagazer:

I agree with your assessment of the little tube worms — it’s pretty unlikely that they have anything to do with the scratching of your young seahorses.

If you see no sign of hydroids, then ectoparasites are probably at fault, most likely some sort of protozoan parasites. The different treatment options we discussed for eliminating such parasites should work well.

No new news on the book to report. Christopher Reggio, the new publisher at TFH, tells me they are still reassessing the market for a major new book about seahorses. One way or another, I expect it to come out this year.

Best of luck with your itchy juveniles, Seagazer! Keep me posted regarding what treatment you feel is warranted, and I can provide you with additional instructions as needed.

Respectfully,
Pete Giwojna