Dear Elizabeth:

Pete Giwojna

Dear Elizabeth:

Judging from your description, it appears that your six-week juveniles are suffering due to an outbreak of nematodes. These pesky little worms are especially troublesome for dwarf seahorses and juveniles of the larger species, and the type of scratching you have noticed is very typical of the irritation and damage the nematodes can do.

In cases like this, I normally recommend administering a quick formalin bath to provide the affected seahorses with immediate relief, followed by treating the aquarium with a good anthelminthic agent such as fenbendazole (brand name Panacur) to eliminate all of the little worms.

Nematodes are tiny, worm-like ectoparasites (i.e., external parasites) that attack the skin and underlying muscle of the affected seahorse, and also invade the gills when there is a heavy infestation.

The most common symptoms are increased respiration or labored breathing and a progressive loss of prehensility in the tail of the seahorse, accompanied by depigmentation (whitening) of the affected areas of the tail. But I should point out that respiratory distress may not be involved in cases when the nematodes have not yet invaded the gills, and that twitching and scratching are typically seen in the later stages of an infestation.

The early symptoms of a nematode infestation are thus increased respirations and a progressive loss of prehensility in the tail of the seahorse. As the tail of the seahorse loses its ability to grasp or cling to objects, the seahorses either swim or sort of slither along the bottom or the substrate with their tails extended stiffly behind them.

Rapid breathing is sometimes the first symptom of an infestation. Flaring gills and extremely labored breathing will signal their obvious distress. The diligent hobbyist will often realize something is wrong at this point, but checking the water parameters will reveal nothing amiss.

Next, the seahorses’ tails will be affected. First they will become colorless and rigid at the very tip and lose their grasping ability in that small segment of the tail. Then the stiffness and loss of coloration will progress a little higher on the tail day by day, until the entire tail is affected, becoming a useless weight that the seahorses must drag around like an anchor when swimming. The loss of flexibility in the tail is apparently the result of the tiny worms boring into the musculature of the tail.

In a heavy infestation, the nematodes will invade the gills, causing respiratory distress, and they may also spread from the gills into the buccal cavity and snout of the seahorse. When that happens, you may also see the characteristic loss of coloration or depigmentation in the snout of the seahorse, together with the usual scratching or twitching, of course …

Here is an excerpt from the biological profile on the lined seahorse (Hippocampus erectus) from the Ichthyology Department at the Florida Museum of Natural History:

· Parasites
Captive lined seahorses are especially vulnerable to parasitic infections including microsporidians, including Glugea heraldi; a myxosporidian of the genus Sphaeromyxa; fungi; ciliates, including Uronema marinum; and nematodes.

Most cases of nematode infestation I have seen involve wild-caught dwarf seahorses (Hippocampus zosterae), but the above reference clearly indicates that the larger breeds of seahorses such as Hippocampus erectus are also susceptible to parasitic nematodes.

As I mentioned earlier, administering a formalin bath will provide the affected seahorses with some quick relief, Elizabeth.

You can then confirm the diagnosis by a close examination of the water in which you administered the formalin baths afterwards:

In a heavy infestation, the nematodes that have been killed during the therapeutic dip/bath will be easily visible in the water using an 8 – 10 X magnifying glass or jeweler’s loupe, and can often be seen with the naked eye.

Fortunately, the distinctive symptoms make nematodes easy to diagnose and easy to cure.

Formalin dips and baths are very effective at eliminating nematodes, Elizabeth, and I recommend that you administer a formalin bath to your foals immediately in order to provide them with some quick relief. Here’s how to proceed:

Formalin Baths

Formalin (HCHO) is basically a 37% solution of formaldehyde and water. It is a potent external fungicide, external protozoacide, and antiparasitic, and is thus an effective medication for eradicating external parasites, treating fungal lesions, and reducing the swelling from such infections. It is a wonder drug for treating cases of Popeye caused by trematodes, and also eradicates external nematodes.

In my experience, provided it is administered properly, seahorses tolerate treatment with formalin very well at therapeutic dosages. For a long term bath the correct dose is 15 to 25 mg/L. [Note: 25 mg/L equals 1 ml (cc) of 37% formalin per 10 gallons of water.] This is done every other day for 3 treatments.

For a short term bath (dip) the correct dose is 250 mg/L. This would equal 1 ml (cc) of 37% formalin per 1 gallon of water. This should be for about 45 minutes to 1 hour. In my opinion, formalin is a safe, effective treatment for parasitic infections in seahorses providing you don’t exceed these dosages and observe the following precautions for administering the medication properly:

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 go to top Chemical Laboratories. Or whatever brand of formalin is available at your fish store should work fine, Elizabeth.

A formalin bath simply involves immersing the seahorse in a container of saltwater which contains the proper dosage of formalin for a period of 30-60 minutes before transferring it to your hospital 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 30 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, Elizabeth, these are the instructions you should follow for your formalin dip:

(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, see the following web page:

Click here: KPD-54 Formalin-3

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) or follow the following directions, courtesy of Ann at the org:

FORMALIN Short-Term BATH Dosage and Preparation Instructions
Active Ingredient: 37% Formaldehyde
Indication: external parasites
Brand Names: Formalin, Formalin-MS
1. Do NOT use Formalin that has a white residue at the bottom of the bottle. White residue
indicates the presence of Paraformaldehyde which is very toxic.
2. “Formalin 3” by Kordon contains only 3% Formaldehyde. Dosing instructions will need to be modified if using this product.
• Fill a small tank with aged, aerated, dechlorinated marine water. Match the pH, temperature, and salinity to that of the tank the Seahorse is currently in.
• Add an artifical hitch and 1-2 vigorously bubbling airlines. Formalin reduces dissolved O2 so heavy aeration is required.
• Add 1ml/cc of Formalin per one gallon (3.8 liters) of tank water. Allow several minutes for the Formalin to disperse.
• Place the Seahorse into the dip water for 45-60 minutes unless it is showing signs of an adverse reaction. If the Seahorse cannot tolerate the Formalin dip, immediately move it back to the hospital tank.
• Observe the Seahorse for 24hrs for signs of improvement.

The formalin baths will provide affected seahorses with some immediate relief from the nematodes, Elizabeth, but they will not cure the problem because the seahorses can be reinfested once they are returned to the nursery tank, or due to the fact that other nematodes may be present in large numbers in the substrate of the aquarium. So you will need to take other measures to eliminate the parasitic worms from the nursery tank and the associated filters as soon as possible.

A relatively light infestation of nematodes can be brought under control via a 50 percent water change, combined with vacuuming the substrate and a thorough tank cleanup. Serious infestations require more drastic measures. A bad nematode invasion will require treating the main tank with a good anthelmintic or deworming agent such as fenbendazole (brand name Panacur).

Worms of all kinds can be controlled in the aquarium by using a medication known as fenbendazole to treat the tank over a period of days. Fenbendazole (brand name Panacur) is an inexpensive anthelmintic agent (dewormer) used for large animals such as horses, and the de-worming granules can be obtained without a prescription from stores that carry agricultural products (e.g., farm and ranch equipment, farming supplies and products, veterinary supplies, livestock and horse supplies, livestock and horse feed). If you live in a rural area, those would be good places to obtain it as well.

You can also fenbendazole granules in small quantities online from the following vendor:

However, there are a couple of things you should keep in mind when treating an aquarium with fenbendazole, Elizabeth. Administering a regimen of fenbendazole (FBZ) or Panacur will eradicate any hydroids, Aiptasia rock anemones, bristleworms, or roundworms (e.g., nematodes) from live rock or live sand, thereby rendering them completely seahorse safe. The recommended dose is 1/8 teaspoon of the horse dewormer granules (22.2% fenbendazole) per 10 gallons of water. Dose aquarium with 1/8 teaspoon/10 gallons every other day until you have administered a total of 3 such treatments (Liisa Coit, pers. com.). Even one dose will usually do a fine job of eradicating worms of all kinds, but Aiptasia rock anemones and hydroids are a bit tougher and may require 2-3 doses to eliminate entirely.

Because fenbendazole is essentially a de-worming agent, it will destroy any bristleworms, flat worms, roundworms or nematodes, spaghetti worms or the like. Unfortunately, this includes desirable worms such as featherdusters, tubeworms, Christmas tree worms, or fanworms as well..

Fenbendazole does not have any adverse effects on biological filtration, but be aware that it is death to many Cnidarians besides hydroids. Mushrooms and related corals are generally not affected, but expect it to have dire effects on other corals (e.g., sinularias), polyps, gorgonians, and anemones. In general, any Cnidarians with polyps that resemble the stalked family of Hydrozoans are likely to be hit hard by fenbendazole, so don’t use this treatment in a reef tank!

Also be aware that fenbendazole seems to soak into the porous live rock and be absorbed indefinitely. I know one hobbyist who transferred a small piece of live rock that had been treated with fenbendazole (Panacur) months earlier into a reef tank, where it killed the resident starfish and Astrea snails. So enough of the medication may be retained within treated live rock to impact sensitive animals months after the fenbendazole was administered. Don’t treat live rock intended for reef systems with fenbendazole (Panacur)!

At the lower dosage recommended for nursery tanks and dwarf seahorse tanks with fry (1/16 tsp. per 10 gallons), fenbendazole normally does not harm cleaner shrimp and decorative shrimp. With the exception of Astrids (Astrea), Coit and Worden have found it does not usually affect the types of snails typically used as cleanup crews (e.g., Nassarius, Ceriths, and Nerites). It will kill starfish but copepods, hermit crabs, and shrimp are normally not affected.

Macroalgae such as the feathery or long-bladed varieties of Caulerpa or Hawaiian Ogo (Gracilaria) are not harmed by exposure to fenbendazole at even triple the normal dose. In fact, if you will be using Caulerpa in your nursery tanks to provide hitching posts for the fry and serve as a form of natural filtration, it’s a very wise precaution indeed to treat them with a regimen of fenbendazole beforehand.

So fenbendazole (FBZ) or Panacur is primarily useful for ridding bare-bottomed nursery tanks and dwarf seahorses setups of hyrdroids and Aiptasia anemones, ridding Caulerpa and other macroalge of hydroids or Aiptasia before its goes into the aquarium, and cleansing live rock of bristleworms, hydroids, and Aiptasia rock anemones before it is introduced to the aquarium.

It can also be used to eradicate bristleworms, roundworms/nematodes, hydroids, an Aiptasia from an established aquarium if it does not house sensitive animals such as live corals and gorgonians, starfish, certain snails, or tubeworms and other desirable worms that may be harmed by FBZ, providing you monitor the ammonia levels closely and are prepared to deal with the ammonia spike that may result from the sudden death of the worm population.

When it comes to snails, Nerites, Ceriths, and Nassarius snails are not affected by the medication and can remain in the aquarium during and after treatment with fenbendazole.

On the other hand, Trochus or turbo snails, Astrea snails, and especially Margarita snails are sensitive to fenbendazole/Panacur and should be removed from the aquarium until the treatment regimen has been completed and the fenbendazole has been pulled from the aquarium using activated carbon and/or polyfilter pads for chemical filtration.

Okay, Elizabeth, that’s the rundown on treating an aquarium with fenbendazole or Panacur.

I would recommend that you perform a 50% water change nursery tank, combined with vacuuming or siphoning the substrate along with the general aquarium cleaning in order to remove as many of the nematodes as possible. Keep the sponge filter and HOB filter running throughout the fenbendazole treatment regimen so that the medication will also kill any nematodes that may have infested the filters themselves, but be sure to remove any activated carbon or other chemical filtration media from the filters so that it doesn’t pull out the fenbendazole. At the same time, give all of the affected seahorses a formalin bath to remove the nematodes they are carrying and provide them with some quick relief.

Since the water changes and thorough aquarium cleaning often do not sufficiently eradicate the nematodes by themselves, you will also need to treat your seahorse tank with the fenbendazole (brand name Panacur) to eliminate the nematodes after temporarily removing any sensitive invertebrates such as certain snails or featherdusters. The juvenile seahorses can remain in the aquarium while it is treated with the fenbendazole, since it has no effect on them at the recommended dosages, and will help to kill any remaining nematodes the ponies may be carrying.

Best of luck resolving this problem, Elizabeth.

Pete Giwojna, Ocean Rider Tech Support

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