Yes, I agree — if your male seahorse is eating well yet losing weight anyway, it’s a good precaution to treat him for internal parasites. Either praziquantel, fenbendazole (brand name Panacur), or maybe metronidazole would be a good choice for such a procedure. None of these medications will have a negative impact on the beneficial nitrifying bacteria that perform biological filtration, so you can administer the medications directly to your seahorse tank providing it houses no delicate invertebrates that could be harmed by the antiparasitic medications.
Aside from intramuscular injections, perhaps the most effective way to administer any of these medications is to gut load adult brine shrimp with them, and then feed the medicated brine shrimp to your seahorses. That’s a very stressful-free way to deworm them and treat them for internal parasites since they can be treated in the main tank where they are the most comfortable and relaxed, in the company of their mates/tankmates amidst familiar surroundings, with no handling necessary.
Gutloading simply means to fill live shrimp up with medication by feeding them food that’s been soaked in the desired medication. Once the feeder shrimp are full of the medicated food — that is, their guts are loaded with it — they are immediately fed to the seahorses, which thus consume the medication along with the shrimp. It’s a neat way to trick seahorses into taking their medicine, just as our moms used to do when were little, crushing up pills in a spoonful of jelly or jam. Another term for gutloading is bioencapsulation, since the medication is neatly contained within a living organism rather than a capsule.
Metronidazole is an antibiotic with antiprotozoal properties that is very effective in eradicating internal parasites in general and intestinal flagellates in particular (Kaptur, 2004). It is ideal for this because it is rapidly absorbed from the GI tract, has anti-inflammatory effects in the bowel, and was designed specifically to treat protozoal infections and anaerobic bacterial infections by disrupting their DNA (Kaptur, 2004).
There are a number of ways to gutload shrimp, but the one described below is one of the easiest and works great for administering metronidazole orally. It is impossible to determine precisely what dosage of medication each individual fish ingests when gutloading, but metronidazole is a very, very safe drug and you cannot overdose a seahorse using this method of treatment. Feeding each seahorse its fill of shrimp gut-loaded with metronidazole for 5-10 days assures that they receive an effective dose of the medication.
I prefer live adult brine shrimp (Artemia sp.) since they are inexpensive, readily available, easy to bioencapsulate, and can be gut loaded in freshwater as described below. To medicate the brine shrimp, dissolve approximately 100 mg of metronidazole per liter or about 400 mg per gallon of water and soak the shrimp in the resulting freshwater solution. If the metronidazole you are using comes in liquid or capsule(powder) form, you can use it as is. But if the metronidazole is in tablet form, be sure to crush it into a very fine powder (you may have to use a household blender to get it fine enough) and dissolve it in freshwater at the dosage suggested above. Soak the adult shrimp in freshwater treated with the antibiotic for 15-30 minutes and then feed the medicated shrimp to your seahorses immediately. (Don’t let your pumps and filters "eat" all the brine shrimp!)
The brine shrimp are soaked in freshwater, not saltwater, because in theory the increased osmotic pressure of the freshwater helps the antibiotic solution move into their bodies via osmosis. But in fact nobody knows for sure whether the antibiotic is diffusing into the brine shrimp or they are ingesting it in very fine particles (brine shrimp are filter feeders and will take in whatever is suspended in the water with them) or whether the brine shrimp merely become coated with the antibiotic while they are soaking in it. But that’s not important — all that really matters is that gut-loading adult brine shrimp with medications this way is effective.
Keep the seahorses on a strict diet of such medicated brine shrimp throughout the treatment period to get as much of the antibiotic into the seahorses as possible, and mix up a new batch of medicated freshwater to soak the brine shrimp in for each feeding.
As an alternative to gut loading or bioencapsulation of the medication, the metronidazole solution can also be injected into freshly killed ghost shrimp, Hawaiian volcano shrimp (red feeder 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.
In addition, Tammy, here are Tracey Warland’s instructions for gutloading brine shrimp with metronidazole or other anti-parasitic medications:
Metronidazole, is one of the low impact parasite meds, it is often hard to overdose on this med, there are however more effective meds that can be used. Praziquantel (by droncit, available at most vets) is a better more effective med.
With parasite meds I usually use about (liquid form) 2.5 mls to 1000 mls, place adult artemia in the solution for about 30 minutes, rinse and fed out 5 days in a row, leave for 2 weeks and retreat for 5 days.
If the med you have is in tablet form they are usually 100mg tablets, crush one to a very fine powder, you may even have to blend it in a household blender to get it fine enough for the artemia to eat and add this to 1000 mls (1 litre) and repeat as above.
Unfortunately eating well and not gaining weight is one of the classic signs of internal parasites.
I would remove her from the tank to feed out the medicated food to ensure she gets the majority of them and it would not hurt to feed out the food to the others also.
Most parasite meds are death to inverts so it is wise to feed them out in isolation.
Happy Seahorse Keeping
As you can see, Tammy, the exact dosage of metronidazole to use when gutloading or injecting shrimp is not crucial at all. It’s a very safe medication that you really cannot overdose via gutloading.
If the affected seahorse is no longer eating, are simply not interested in adult brine shrimp, then it should be treated with the medication in a hospital tank (no carbon filtration). Since metronidazole is only active against anaerobic bacteria, it will not affect beneficial Nitrosomonas and Nitrobacter species, and you can thus maintain biological filtration in the hospital tank throughout treatment (Kaptur, 2004). Dissolve 250 mg of metronidazole for every 10 gallons of water in the hospital tank, and the medication will be absorbed through the seahorse’s gills (Kaptur, 2004). For best results with tropical seahorses, raise the water temperature in the treatment tank to 78°F-80°F and be sure to increase aeration and circulation accordingly, since the water will hold less dissolved oxygen at elevated temps (Kaptur, 2004). To compensate for this, it’s a good idea to add an extra airstone and/or enough methylene blue to tinge the water bluish (Giwojna, Dec. 2003). Metronidazole is designed to work best at human body temp (Kaptur, 2004), and raising the temperature of the hospital tank as high as possible within their comfort range of the seahorses markedly increases the effectiveness of the medication. Stay on top of the water quality in the treatment tank with water changes as necessary, and redose the tank with a full dose of metronidazole daily regardless of how much water was changed (Giwojna, Dec. 2003). (Metronidazole is oxidized over a period of several hours, so the entire dose needs to be replenished daily; Kaptur, 2004.) Treat the affected seahorse in isolation for a minimum of 5 consecutive days.
[CAUTION! When treating with metronidazole, elevate the water temp for tropical species only! Never take temperate or subtemperate species out of their comfort zone with regard to temperature. Doing so will be stressful and do far more harm than good, even when treating them for intestinal parasites with metronidazole.]
When administered properly, metronidazole is wonderfully effective at eliminating intestinal parasites, and there should be signs of improvement within 3 days of treatment (Kaptur, 2004). The seahorse’s appetite should pick up, and as it does, those characteristic white stringy feces will return to normal (Giwojna, Dec. 2003).
In summation, if the seahorses are still eating, administering the metronidazole orally via gut-loaded shrimp is often extremely effective (Giwojna, Dec. 2003). With anti-parasitic medications such as praziquantel and metronidazole in liquid form, this can be accomplished by using 2.5 mls of the medication to 1000 mls of freshwater, soaking adult brine shrimp (Artemia spp.) in the solution for about 30 minutes, and then feeding them to the seahorses for 5 days in a row, and then repeating the same treatment again two weeks later.
[Note: 20 drops equals 1 ml, so 50 drops of the medication equals 2.5 mL (20 drops/ml x 2.5ml = 50 drops). Also 1000 mls equals ~ 1 quart, so in order to gut load the adult brine shrimp with the liquid form of the medication, you would place 50 drops of the medication in a quart of saltwater and soak the brine shrimp in that for half an hour before feeding it to your seahorses.
Intramuscular injections of metronidazole at a dosage of 50mg/kg repeated every 72 hours for a total of 3 treatments are also extremely effective in treating internal parasites, but in most cases this is impractical for the home hobbyist.
If you have the liquid form of praziquantel (Prazi Pro) you can gutload the adult Artemia and bioencapsulate the medication in the same manner as liquid metronidazole. Just mix 2.5 mls of the liquid praziquantel to 1000 mls of water, soak the adult brine shrimp (Artemia spp.) in the resulting solution for about 30 minutes, and then feed them to the seahorses for 5 days in a row, and then repeat the same treatment regimen again two weeks later.
You can use either saltwater from your aquarium or dechlorinated freshwater for dissolving the liquid praziquantel and soaking the adult brine shrimp, but again I prefer to use the freshwater since that may help the adult Artemia to absorb more of the medication and the freshwater also helps to disinfect the live brine shrimp while they are soaking.
Praziquantel can also be administered as a bath either at 10ppm for 3 hours or at 1ppm for 24 hours. However, anti-parasitic medications are generally tough on invertebrates in general, and if your seahorse setup includes sensitive invertebrates, it would be much better to administer the medications orally as previously discussed or to treat the seahorses in a hospital tank where the inverts won’t be affected.
Adult brine shrimp can also be gut-loaded with fenbendazole (Panacur) by soaking them in 250mg Panacur /kg food and then feeding the medicated brine shrimp to the seahorses for three consecutive days. Repeat the three-day treatment regimen again one week later. As you know, fenbendazole is an anthelmintic agent or dewormer, and if you suspect your seahorse has a problem with cestodes or roundworms, as indicated in your post, then Panacur should be included as part of your treatment regimen.
Or you can administer the Panacur as a bath instead, as explained in the post on this page titled "Hydroids!"
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, as well as praziquantel in liquid form and metronidazole from the following vendor:
However, there are a couple of things you should keep in mind when treating an aquarium with fenbendazole. Administering a regimen of fenbendazole (FBZ) or Panacur will eradicate any hydroids, Aiptasia rock anemones, or bristleworms 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 do a fine job of eradicating bristeworms, 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, spaghetti worms or the like. The FBZ or Panacur treatments are best administered to the live rock in a bucket or hospital tank before the LR is introduced in the main tank. Otherwise, the massive die-off of the worm population in the aquarium may require large water changes in order to prevent a dangerous ammonia spike! And after the treatment is completed, its a good idea to add a portion of newly purchased live sand to the system in order to help restore its normal diversity of fauna and microfauna again (Liisa Coit, pers. com.).
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 and other echinoderms 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 aside from being an effective dewormer, 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, hydroids, an Aiptasia from an established aquarium if it does not house sensitive animals such as live corals and gorgonians, starfish, Astrea 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.
In your case, Tammy, I would recommend praziquantel or fenbendazole (Panacur) over the metronidazole. For best results, you might consider treating your male first with praziquantel, as outlined above, and then follow that up with a regimen of Panacur.
Best of luck eradicating any internal parasites from your skinny stallion! Here’s hoping that he fattens up nicely in the near future.