Pete Giwojna

Dear Kwang-seek Choi:

Courtship in many temperate and subtemperate seahorses is dominated by pouch displays. Cold-water species such as the Big Belly Seahorse (Hippocampus abdominalis) typically engage in a different type of pouch display known as “Ballooning.” This is a simple display in which they inflate their brood pouches to the fullest possible extent and parade around in front of the female in all their glory as though trying to impress her with the sheer dimensions of their pouches. The pumped up paramours perform proudly, putting on quite a show for the flirtatious fillies.

In your case, Kwang-seek Choi, I suspect that the continued swelling of the brood pouch, or nursery bag, as you call it, is such a courtship display, since Hippocampus abdominalis males typically deliver large broods of young rather than a single offspring.

But a pregnant male will sometimes release one or two newborns prematurely and then temporarily suspend the birthing process, only to deliver the rest of his brood a day or two later, so that’s also a possibility.

However, I don’t believe that your Big Belly Seahorse has excess gas bubbles building up in his “nursery bag” because that would result in positive buoyancy and he would be floating as a result.

Best of luck breeding your seahorses, Kwang-seek Choi.

Respectfully,
Pete Giwojna, Ocean Rider Tech Support

Dear Kevin:

Thank you for your kind words, sir! If you ever need any in-depth help with any seahorse-related issues please don’t hesitate to contact me via the discussion forum or via personal e-mail, Kevin. You can always reach me at the following e-mail address:

[email protected]

Best wishes with all your fishes, sir!

Respectfully,
Pete Giwojna, Ocean Rider Tech Support

Dear Chris:

I’m sorry to hear about the problems you are having with some of your seahorses. It’s very difficult to determine what is going on with your ponies from afar with so little to go on, but the seahorse that is “playing dead” curled up on the bottom and slithering around with labored breathing and no appetite sounds very much like it could be suffering from ammonia poisoning or nitrite toxicity, so I suggest that you check your water quality parameters immediately to see if there has been a spike in the ammonia or nitrate levels.

The most obvious symptoms of ammonia poisoning/nitrite toxicity are a loss of equilibrium, hyperexcitability, increased respiration and oxygen uptake, and increased heart rate. At extreme ammonia levels, fish may experience convulsions, coma, and death. Seahorses exposed to less extreme ammonia levels will struggle to breathe. They will be lethargic and exhibit rapid respiration. They may appear disoriented, periodically detaching from their hitching posts only to sink to the bottom.

In significant cases, you will often see the affected seahorses lying prone on the bottom unable to right themselves at all for extended periods, blindly bumping into objects on the walls of the aquarium in complete disorientation, and going into actual convulsions, accompanied by severe respiratory distress.

Ammonia poisoning is completely reversible providing the seahorses weren’t exposed to toxic levels for too long, and the best first aid you can provide for ammonia poisoning is to immediately transfer the seahorses into clean, well-aerated saltwater with zero ammonia and zero nitrite aquarium. (In your case, Chris, if the ammonia levels or nitrite levels in the aquarium are elevated, perform a major water change using freshly mixed saltwater that has been detoxified and preadjusted to the same specific gravity and water temperature as your seahorse tank, and then dose the aquarium with SeaChem Stability to boost the biological filtration.)

Exposure to moderate levels of ammonia and nitrite (or excessively high levels of nitrates) can change the normal hemoglobin in the seahorse’s blood stream to a form (i.e., methhemoglobin) that is no longer able to transport oxygen. If this becomes severe enough, it will leave the affected seahorse starved for oxygen, which makes it very weak and fatigued. As a result, the affected seahorses may detach themselves from their hitching posts periodically and rest on the bottom, unable to exert themselves in their weakened condition. As you can imagine, being deprived of oxygen really wipes them out in terms of loss of energy and stamina. And it also results in respiratory distress, and rapid, labored breathing as they try to oxygenate themselves and compensate for the lack of normal hemoglobin.

One of the properties of methylene blue is that it can reverse this process and convert the methhemoglobin in the red blood cells back into normal hemoglobin, which can then pick up and transport oxygen again as usual. That’s why it is so helpful in relieving shipping stress and treating ammonia exposure and nitrite poisoning. For this reason, you may want to pick up some methylene blue at your local fish store and keep it on hand in case it is ever needed (the Kordon brand of methylene blue is best, in my opinion).

The usual criteria for determining whether or not methylene blue is needed to help seahorses recover from exposure to high levels of ammonia is their respiration. If the seahorse has labored breathing — huffing or rapid respiration — then methylene blue is called for. Likewise, if the seahorse is experiencing convulsions or its behavior otherwise indicates it is suffering from more than temporary disorientation and loss of equilibrium, such as lying prostrate on the bottom, unable to right itself again at all after two or three hours have passed, it may benefit from methylene blue to assist its recovery.

When that’s the case, hobbyists may want to consider a quick dip in methylene blue. Commonly known as “meth blue” or simply “blue,” this is a wonderful medication for reversing the toxic effects of ammonia and nitrite poisoning. Methylene blue transports oxygen and aids breathing. It facilitates oxygen transport, helping fish breathe more easily by converting methemoglobin to hemoglobin — the normal oxygen carrying component of fish blood, thus allowing more oxygen to be carried through the bloodstream. This makes it very useful for treating gill infections, low oxygen levels, or anytime your seahorses are breathing rapidly and experiencing respiratory distress. It is the drug of choice for treating hypoxic emergencies of any kind with your fish. However, methylene blue will destroy nitrifying bacteria so it should be used in a hospital tank or as a brief bath or dip only (if used in an established aquarium, it will impair the biological filtration and the tank may need to be cycled all over again).

Here is some more information that may be helpful if you ever need to treat with methylene blue, for any reason:

If you can obtain the Kordon brand of Methylene Blue (available at most well-stocked local fish stores), there are instructions for administering it as a very brief, concentrated dip are as follows:

For use as a dip for treatment of fungus or external parasitic protozoans and cyanide poisoning:
(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.

When you administer such a dip, hold the seahorse in your hand throughout the procedure and time it closely so that the dip does not exceed 10 seconds.

And here are Kordon’s instructions for administering the methylene blue in a hospital tank if longer-term treatment seems appropriate to reverse more severe cases of nitrite poisoning and ammonia toxicity:

As an aid in reversal of nitrite (NO2-) or cyanide (CN-) poisoning of marine and freshwater aquarium fishes:
(a) Remove carbon filter and continue to operate with mechanical filter media throughout the treatment period.
(b) Add 1 teaspoon of 2.303% Methylene Blue per 10 gallons of water. This produces a concentration of 3 ppm. Continue the treatment for 3 to 5 days.
(c) Make a water change as noted and replace the filter carbon at the conclusion of the treatment.

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

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

If you obtained a brand of methylene blue other than Kordon, just follow the instructions the medication comes with.

Just be sure that you don’t have the methylene blue to your main tank, since that can have a negative impact on the biological filtration.

If you can provide me with photographs, that could also help be in diagnosing this problem, Chris. You can contact me off list at the following e-mail address and attach any photos that might be helpful to your e-mail:

[email protected]

Good luck in the meantime.

Respectfully,
Pete Giwojna, Ocean Rider Tech Support

Dear hobbyist:

I understand that you have a seahorse that seems to be having seizures, and that darkens in coloration where it is experiencing these seizures.

After examining the video you provided, the spasmodic movements of the seahorse are similar to the muscular contractions that a pregnant seahorse undergoes when giving birth. However, the seahorse in the video appears to be a young female, so its contortions are clearly not birth spasms.

It is possible for seahorses to exhibit seizure-like symptoms when they have suffered brain damage or a head injury or when they had been exposed to toxic substances.

For example, we sometimes see neurological symptoms like that under hypoxic conditions when seahorses have been deprived of oxygen for too long.

Erratic behavior, neurological symptoms, and seizures can also result when a seahorse is suffering from major organ failure, particularly if the liver and/or kidneys are involved. Seahorses have primitive aglomerular (having tubules but no glomeruli) kidneys, whose primary function is to filter waste from the blood (Evans, 1998). The seahorse’s kidneys are also hard at work maintaining its blood and tissues at the proper osmotic concentration at all times (Seahorse Anatomy, 2004). This is necessary because seahorses live in seawater that is four times saltier than their blood and body fluids, and they are constantly losing water via osmosis across their gills, through their skin, and in their urine as a result (Kollman, 1998). Marine fish risk dehydration because salt cannot diffuse into their bodies but water is being continual lost to the concentrated seawater that surrounds them ((Kollman, 1998).

To compensate for this, marine fish drink seawater continuously to replace lost fluids and then excrete the excess salts they have taken in through the kidneys, in their feces, and from their gills (Kollman, 1998). As a result, their kidneys produce a very concentrated, salty urine (Kollman, 1998). Expelling excess salt this way is very energetically demanding and comes at a high metabolic cost because the salts must be pumped out of their bodies against a strong pressure gradient (Kollman, 1998).

If your female’s kidneys have failed or been impaired as a result of an infection of some sort, she could be suffering from dehydration or a buildup of toxins in her system, either of which could cause the sort of seizure-like behavior and symptoms your female is now displaying.

The seahorse’s liver is also different than that of other vertebrates. Like many fishes, seahorses do not have a separate pancreas. Instead pancreatic tissue is dispersed throughout the liver, which thus performs double duty, carrying out the functions of both the liver and the pancreas (Seahorse Anatomy, 2004). For this reason, the fish liver is usually referred to as the hepatopancreas. The seahorse’s hepatopancreas is basically a big digestive gland (Seahorse Anatomy, 2004). It is a large organ that secretes enzymes and produces bile to aid in digestion and food absorption. It also stores food energy in the form of glycogen and plays a vital role in the detoxification of blood. If your seahorse’s liver was impaired and can no longer perform that role, toxins would again build up in the blood and tissue of your seahorse and could then cause the sort of symptoms your female is showing once they build up past a certain point. The most common cause of such liver problems is hepatic lipidosis or fatty liver disease.

Because of their lazy lifestyle, captive seahorses that are feed a diet that’s excessively rich in HUFA (highly unsaturated fatty acids) and other lipids are vulnerable to a debilitating affliction commonly known as “fatty liver disease” or hepatic lipidosis. When the seahorse’s liver or hepatopancreas becomes infiltrated with fatty deposits as a result of hepatic lipidosis, it interferes with the organ’s ability to perform these vital functions and that has dire consequences for the affected seahorse.

If your female was an old warhorse that’s getting up in years, such problems with her liver or kidneys could simply be the result of the inevitable aging process. The aging process is always associated with increased morbidity and mortality, and seahorses are no exception to be sure. As seahorses age, they become increasingly vulnerable to certain conditions that did not trouble them when they were younger. This often manifests itself as an increased incidence of gas bubble disease (particularly pouch emphysema and subcutaneous emphysema), chronic wasting, and certain types of cancers. For example, I know of several older seahorses that developed malignant neoplasms, including tumors of the small intestine with liver metastasis and a case of a fibrosarcoma of the pouch. Specimens with anorexia and chronic wasting often have distended gall bladders, fatty livers, and sunken eyes.

Hepatic lipidosis in the most common of these age-related conditions. Of all the necropsies Dr. Martin Belli has performed on hobbyist’s seahorses, fully 38% of them had fatty livers (Belli, per. com.).

As I mentioned, because of their sedentary lifestyle, our galloping gourmets are susceptible to this debilitating affliction when they are given a diet that’s excessively rich in HUFA (highly unsaturated fatty acids) and other lipids. Mature seahorses that are no longer breeding are at greatest risk from hepatic lipidosis. Young seahorses need a high-fat diet to sustain their rapid growth and development, and breeding pairs that are churning out brood after brood of fry likewise need all the energy they can get. But once they reach sexual maturity, their growth rate slows markedly, and nonbreeding adults that receive a high-fat diet will begin to store excess fat in specialized cells called adipose tissue (Tamaru, Sep. 2001). Eventually these fatty deposits will begin to infiltrate the liver cells, hence the name fatty liver disease (Tamaru, Sep. 2001).

In severe cases, adipose tissue can become so thick that it can literally hides the internal organs, cloaking them within a cocoon of fat, and distending the abdomen (Tamaru, Sep. 2001). When the seahorse’s liver or hepatopancreas becomes badly infiltrated with fatty deposits, it interferes with the organ’s ability to perform its vital role in digestion, food absorption, and detoxification of the blood, which can result in the sort of unusual behavior and seizure-like symptoms your female is suffering from.

Hepatic lipidosis is one of those conditions you can’t do much about after the fact, so the best way to address such problems is to concentrate on preventing them in the first place. Avoiding overfeeding, fasting adults once a week and using relatively low-fat enrichment products such as Vibrance II for mature seahorses that are no longer breeding are simple ways to prevent fatty liver disease.

In summation, those are some of the things that can cause seahorses to exhibit seizure-like behavior, but I don’t know of any of them apply in your case. I’m very sorry I could not be more helpful in this instance.

Respectfully,
Pete Giwojna, Ocean Rider Tech Support

Dear Stephanie:

I am sorry to hear about the problem that your female SunFire has been experiencing. She is clearly having a problem with negative buoyancy (i.e., the tendency to sink), which can result from a number of causes, making it very difficult to determine what may be causing her buoyancy problems.

The type of behavior you describe — difficulty in swimming, hanging upside down for long periods, perhaps even laying horizontally on the bottom, and the inability to assume her normal upright posture when perched to a hitching post — could be either an indication of generalized weakness or it could be due to negative buoyancy as the result of swim bladder disease or a buildup of fluid accumulating within her brood pouch or coelomic cavity.

As in many other bony fishes, the seahorse’s gas bladder functions as a swim bladder, providing the lift needed to give them neutral buoyancy. In essence, the swim bladder is a gas-filled bag used to regulate buoyancy. Because the seahorse’s armor-plated body is quite heavy, this organ is large in Hippocampus and extends from the neck well down into the body cavity along the dorsal boundary.

When the swim bladder is inflated with just the right amount of gas, the seahorse achieves neutral buoyancy, which just means that if neither tends to rise or sink. It is thus weightless in the water, with the buoyancy from its gas bladder exactly canceling out the pull of gravity. This facilitates swimming and makes holding its body upright effortless.

But a number of things can disrupt the normal functioning of the gas bladder and the gas gland that inflates it, resulting in either too little or too much gas being secreted into the swimbladder. When too much gas is secreted into the swimbladder the seahorse becomes too buoyant. Hyperinflation of the swimbladder thus results in positive buoyancy and the tendency to float. Likewise, if too little gas is secreted into the swimbladder, exactly the opposite occurs in the seahorse becomes too heavy. Under inflating the gas bladder therefore results in negative buoyancy and the tendency to sink.

The negative buoyancy that results from an underinflated gas bladder makes it difficult for the armor-plated seahorse to swim normally, rise from the bottom, or even hold itself erect. An underinflated swim bladder is sometimes a problem a seahorse can correct on its own, as more gas is gradually secreted into the swim bladder from the gas gland. This is a gradual process and may take days to accomplish. However, if your female has had this problem for a 3 to 4 weeks, then it’s pretty clear that she is not going to be able to correct the problem on her own.

It’s using upside down due to generalized weakness, that can sometimes happen when a seahorse has been unable to eat normally for an extended period of time, sapping its strength. Or it can also be a consequence of old age, Stephanie. SunFires typically reach marketable size around 6-8 months of age, so your female was probably a least that old when you receive care, and if you have had for a few years now, she may be around 4 years old or thereabouts.

So it could well be that your female is simply reaching the end of her natural life span, Stephanie. Certainly the aging process is always associated with increased morbidity and mortality, and seahorses are no exception to be sure. As seahorses age, they become increasingly vulnerable to certain conditions that did not trouble them when they were younger. This often manifests itself as an increased incidence of gas bubble disease (particularly pouch emphysema and subcutaneous emphysema), chronic wasting, and certain types of cancers. For example, I know of several older seahorses that developed malignant neoplasms, including tumors of the small intestine with liver metastasis and a case of a fibrosarcoma of the pouch. Specimens with anorexia and chronic wasting often have distended gall bladders, fatty livers, and sunken eyes. These types of age-related conditions don’t kill suddenly; rather, they debilitate the seahorse over time and it eventually succumbs to disease in its weakened condition.

Hepatic lipidosis in the most common of these age-related conditions. Of all the necropsies Dr. Martin Belli has performed on hobbyist’s seahorses, fully 38% of them had fatty livers (Belli, per. com.).

In my experience, the lifespan of 3-5 years is fairly average for captive-bred-and-raised seahorses in a home aquarist’s tank, Stephanie, so if your female SunFire is around four years old now, it’s quite conceivable that she could be suffering from hepatic lipidosis, impaired renal function, or other age-related conditions and is basically just worn down, on her way out. In that case, there there’s really nothing we can do about it, so let’s assume that her negative buoyancy is caused by something else.

For example, an underinflated gas bladder can also result from infection, and I have seen several cases of swim bladder disease that were associated with internal parasites (digenes), which sometimes also contribute to generalized weakness, so you may want to consider treating the affected seahorse with a good antiparasitic that is effective against internal parasites, such as metronidazole or praziquantel (more about that later in this e-mail).

On the other hand, her negative buoyancy could be associated with a buildup of fluid within the coelomic cavity, which is a problem that is commonly known as abdominal dropsy or ascites in tropical fish. If the female seahorse’s abdomen appears to be bloated or swollen and she is experiencing problems with negative buoyancy, that would seem to indicate a problem with abdominal dropsy or ascites, which would require treatment with the appropriate medication in order to resolve. (Let me know if that’s the case, Stephanie, and I will provide you with a treatment regimen that should be helpful.)

But as we have been discussing, hanging upside down for extended periods could also be an indication of generalized weakness, Stephanie. When that’s the case, the seahorse is too weak to hold itself upright in its normal posture, which can result in the sort of behavior you describe. In seahorses, this sort of generalized weakness is often associated with a lack of oxygen, which can result from insufficient levels of dissolved oxygen in the aquarium water at the bottom of the tank. Low dissolved oxygen levels and high levels of dissolved carbon dioxide can result if there is a lack of surface agitation and/or poor water circulation throughout the aquarium. Many times, this can be corrected simply by increasing the surface agitation and aeration in the aquarium in order to promote better oxygenation and facilitate more efficient gas exchange at the air/water interface.

But oxygen deprivation can also result from spikes in the ammonia or nitrite levels in the aquarium, or even excessively high levels of nitrate. When that happens, the high levels of ammonia/nitrite can convert the hemoglobin in the seahorses red blood cells into a form of the molecule (i.e., methhemoglobin) that is no longer able to transport oxygen. When that’s the case, a seahorse can be starved for oxygen even in an aquarium that has high levels of dissolved oxygen. This is a condition that can correct itself if you can simply eliminate the spike in the ammonia or nitrite levels, or reduce the levels of nitrates to <10 ppm. The best first aid measure for such a problem is to immediately transfer the seahorse into clean saltwater with zero ammonia and zero nitrite. In addition, a quick dip in concentrated methylene blue or a longer bath and less concentrated methylene blue can offer work wonders in such cases because the methylene blue is able to transform methhemoglobin back into the normal hemoglobin molecule, thereby allowing the erythrocytes to transport oxygen normally again. (Note: methylene blue can impair the biological filtration of the aquarium so it should be used as dips or baths, or administered in a hospital tank, rather than being added to the main tank.)

So I would recommend that you check your water chemistry to make sure that the ammonia, nitrite, and nitrate levels are where they should be. If there is any doubt about your water quality, Stephanie’t hesitate to perform one or more water changes to make sure that the water quality is optimal. In the meantime, it would also be advisable to increase the surface agitation and aeration in your seahorse setup in order to assure that the dissolved oxygen levels remain nice and high and that the levels of dissolved carbon dioxide remain low.

Let me know if there has been a spike in the ammonia or nitrite levels – or if the seahorse tank is experiencing excessively high levels of nitrate – and I will provide you with directions for performing a dip or bath methylene blue.

And of course her negative buoyancy can also be resolved of internal parasites (digenes) affecting their gas bladder, which sometimes also contribute to generalized weakness, so you may want to consider treating the affected seahorse with a good antiparasitic that is effective against internal parasites, such as metronidazole or praziquantel.

For example, Aquarium Pharmaceuticals makes a product called General Cure, which contains both metronidazole and Praziquantel, making it ideal for treating internal parasites. Here is some additional information about General Cure and not to use it according to directions, Stephanie:

‹open quote›
General Cure by Aquarium Pharmaceuticals

* Anti-parasitic fish medication rapidly treats a wide variety of parasitic diseases
* Effective fish medication for use in fresh and saltwater aquariums
* Treats diseases such as gill & skin flukes, hole-in-the-head disease, anchor worm, velvet, and fish lice.

Easy-to-use fish medication contains metronidazole and praziquantel in quick-dissolve powder form. Treats a wide variety of parasitic diseases – including velvet, anchor worm, fish lice, hole-in-the-head disease, and gill and skin flukes. Will not color water. For use in both freshwater and saltwater aquariums. Each packet doses 10 gallons. Economical 850 gram bulk jar doses up to 3,270 gallons and includes a 1 tsp scoop.
Packets
Active Ingredients: 250 mg Metronidazole and 75 mg Praziquantel per packet.
Directions for Use: For best results, remove activated carbon or filter cartridge from filter and continue aeration. For each 10 gallons (38 L) of water, empty one packet directly into aquarium. Repeat dose after 48 hours. Wait another 48 hours then change 25% of the aquarium water and add fresh activated carbon or replace filter cartridge.
This package treats up to 100 gallons. Two doses required for full course of treatment.
Diagnostic Chart
Gill & Skin Flukes: Very common fish parasites. Can be found on the gills, scales or skin. Not visible without the aid of magnification. Symptoms may include: darkening of skin, clamped fins, excess mucous. Fish may also swim erratically or become emaciated.
Hole-in-the-Head Disease: Symptoms include pitting and erosion of skin and muscle tissue around the face and side of body. Many infected fish exhibit poor appetite, weight loss and nervousness
Anchor Worm: These worms penetrate the skin and embed an anchor-like attachment into the fish. Often a thread-like appendage is all that is visible. Fish tissue is often red at the point of attachment. May be difficult to see without magnification.
Velvet: Heavy infestations cause a golden, velvety appearance or small, white spots on the sides of fish. Gill infestation may cause labored breathing and scratching on objects in the aquarium.
Fish Lice: A parasitic crustacean that can easily hide under the scales or other parts of fish. Fish lice pierce the skin, sucking blood and tissue fluids. Magnification is typically required to see fish lice.
‹close quote›

Metronidazole and Praziquantel won’t have any adverse effects on the beneficial bacteria that provide biological filtration for your aquarium, so they are very safe to use in a fish-only setup. However, some invertebrates can be sensitive to anti-parasitic medications, so if you have a lot of delicate live corals or feather duster worms or decorative shrimp, then you may want to administer the medications in a hospital tank or treatment tank instead of your main tank, Stephanie.

Good luck.

Respectfully,
Pete Giwojna, Ocean Rider Tech Support

Dear Kaie:

Like all cnidarians, hydroids are capable of stinging. There are very many types of hydroids, but the kinds that you cannot feel stinging with your bare hands and forearms are generally harmless to the greater seahorses.

However, some hydroids and hydromedusae can produce a notable sting to your bare skin when you’re working in the aquarium, and such varieties can be a source of irritation to be even the larger seahorse species, so if you have hydroids established in your aquarium and they are one of the varieties with potent nematocysts, it’s possible that they could be stressing your seahorses to the point where their immune system is compromised and they become susceptible to various health problems.

Sooner or later hydroids will appear in any marine aquarium that is receiving regular feedings of rotifers, copepods, or baby brine shrimp or plankton suitable for filter feeding invertebrates. It’s inevitable because they can gain entry into the aquarium in many ways. For example, they are notorious hitchhikers. Both the colonial polyp stage and the free-swimming micro-jellies can thumb a ride on live rock, macroalgae, hitching posts, sand or gravel, specimens of all kinds, or within so much as a single drop of natural seawater (Abbott, 2003). Beware of fuzzy looking seashells! Very often hydrozoans come in on the shells of the hermit crabs or snails we purchase as aquarium janitors (Abbott, 2003). Or they may be introduced with live foods, or even among Artemia cysts, in some cases it seems. They can even be transferred from tank to tank in the aerosol mist arising from an airstone or the bubble stream of a protein skimmer.

It can be very challenging to identify hydroids because there are about a zillion different species of hydrozoans and the different types have different characteristics and are often vary remarkably in appearance. There is considerable variation within the species as well, and the same type of hydroids can appear vastly different depending on the size of the colony and its stage of development, conditions in the aquarium, and their predominant diet. And, of course, the different stages of the life cycle of these amazing animals are so entirely different that they were long believed to be different types of cnidarians altogether, and different species names were often assigned to the same hydroid in different phases of its life cycle. Because they are so difficult to identify and are not easy to distinguished with the naked eye during their initial stages, hydroids often go undetected in nursery and rearing tanks until they begin to take a toll 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). The “snowflake” type of hydroids seem to be particularly common in aquaria, whereas other species look more like crystal chandeliers, and some species form bushy colonies as they grow that serve as microhabitats for Caprellid skeleton shrimp and other tiny crustaceans.

Even a large hydroid colony appears harmless to the naked eye of the untrained observer. It takes a much closer look to reveal the dreaded ‘droid’s lethal nature, as described below:

“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).”

The feeding or nutritive zooids are the distinct individual animals in a hydroid colony that are responsible for capturing and digesting prey; as such, they bear the nematocyst-studded tentacles. But you need high magnification in order to appreciate the true beauty of living hydrozoans, or to differentiate between different species of hydroids, or to observe the zooids going about their deadly business.

Hydroids are insidious because they start out so small and insignificant, yet spread so quickly under ideal conditions (e.g., a nursery tank or dwarf seahorse tank receiving daily feedings of Artemia nauplii). 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.

Once they find their way into a dwarf seahorse setup or nursery tank, hydroids can explode to plague proportions very quickly because conditions are ideal for their growth: perfect temperatures, an abundance of planktonic prey that is renewed every few hours, and a complete absence of predators.

When hydroids become a problem in the nursery or dwarf tank, there are a couple of good ways to eradicate them and get the situation under control again:

Eliminating Hydroids

Hydroids 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:

http://seahorsesource.com/?wpsc-product=fenbendazole-panacur-10-suspension

However, there are a couple of things you should keep in mind when treating an aquarium with fenbendazole, Kaie. 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)!

But this can actually be a good thing in the dwarf seahorse tank. The fenbendazole that soaks into live rock and is then leached back out again in very small quantities can provide the dwarf seahorse tank with protection against another outbreak of hydroids for many months after the tank is treated.

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. It will kill starfish but copepods, hermit crabs, and shrimp are normally not affected.

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.

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 hydroids 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 rock anemones 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 summation, if the aquarium with a hydroid problem will be housing live corals at some point, it would be best not to treat it with fenbendazole. And you may not need to be concerned about the hydroids in the first place, since as long as you keep them out of your nursery tanks, most types of hydroids won’t present a problem for large seahorses like Mustangs and Sunbursts (Hippocampus erectus) at all. They are impervious to their stings. In fact, in the wild, seahorses often encourage algae, small bryozoans and other encrusting organisms, including hydroids, to grow on their exoskeleton in order to enhance their camouflage (Vincent 1990). The hydroids are only a problem for baby seahorses in nursery tanks or for the tiny dwarf seahorses, which are susceptible to their stings. So as long as you will be keeping large seahorses in the aquarium that has hydroids, there is really no need to eliminate them.

If it becomes necessary to eradicate hydroids from an aquarium that will be used for live corals and delicate invertebrates, there is another alternative to killing them with fenbendazole that you can consider. Hydroids of many kinds can be eradicated from the aquarium by raising the water temperature to 92°F or above for period of 3-5 days (Liisa Coit, pers. com.). Keep all of the filters and equipment operating and sterilize your brine shrimp nets, so that the hot water circulates throughout them and destroys any hydroids or hydromedusae that may be present in the filtration system. Be sure to sterilize your brine shrimp nets, etc., at the same time as you are heating up the infested aquarium. (Seahorses and their tankmates, including snails and the cleanup crew, must be removed to a temporary holding tank while the heat treatment is carried out.) Maintaining the water temperature at 92° for this period does not harm the beneficial nitrifying bacteria in your biofilter, injure marine plants or macroalgae, or kill off copepods and other beneficial microfauna (Liisa Coit, pers.com.).

After the treatment period, perform a large water change to assure that the die off of hydroids does not degrade your water quality, and adjust the water temperature back to normal, and all the animals can be returned to the aquarium. The tank will not undergo a “mini cycle” and there will be no ammonia or nitrite spikes (Liisa Coit, pers. com.).

However, not all types of hydroids respond to the heat treatment method of eradication. Unfortunately, the snowflake type of hydroids that are all too common seem to have no difficulty surviving the heat treatment. So generally speaking, then Panacur (i.e., fenbendazole) is a more reliable way to eliminate them. But if your hydroids do not resemble snowflakes, then there is a fair chance that the heat treatment will be effective.

Okay, Kaie, that’s the quick rundown on hydroids and when they need to be controlled.

The problems you could be having could serve may also be an indication that the seahorses provided by your local fish store (LFS) are not the healthiest. It’s possible that your pet-shop ponies may be wild-caught or may have been pen raised, rather than being captive-bred-and-raised seahorses

Net Pens are a low-tech, low-maintenance method of farming seahorses that basically involves raising them in large enclosures in coastal waters. In some cases, entire lagoons may be fenced off for that purpose. In the simplest form of pen rearing, broodstock are released into these enclosures, and then they and their progeny are pretty much allowed to fend for themselves thereafter. Any offspring that survive to marketable size are periodically harvested from the holding pens or lagoons.

Such operations are controversial with environmentalists for a number of reasons. Since the enclosures are open to the ocean, there is a real risk that adults or their fry may escape from the pens and establish colonies in the wild that may pose a threat to endemic seahorse populations. The pens are no barrier to disease organisms or parasites, so pathogens and parasites imported on foreign broodstock may spread to fishes in the wild (or vice versa). Wastes from the high density of penned animals are carried directly to ocean on prevailing tides and currents and may have a negative environmental impact on the surrounding area. There is no way to monitor the penned animals, hence no way to determine whether the seahorses they contain are actually born and raised in captivity or are merely wild-caught seahorses maintained in holding pens prior to being shipped off to unsuspecting consumers.

Pen-grown ponies can thus be risky for the hobbyist because of the circumstances under which they were raised. In essence, a mesh barrier is all that separates them from wild seahorses. There is no guarantee they will be disease free. Although many of them learn to accept frozen Mysis, there is no guarantee they will eat frozen foods since they are often accustomed to foraging for live prey. There is no guarantee they will be able to adjust to aquarium conditions since they are essentially raised in the sea. There is no guarantee that they are even captive bred, since the pens are not secure and livestock is introduced and removed from the pens and lagoons on a continuous basis. There is no guarantee they will be friendly and sociable rather than shying away from their keepers, since they are unaccustomed to the human presence.

Seahorse keepers that are shopping for their livestock at their LFS should therefore proceed with caution nowadays. Don’t assume that the new CITES regulations protecting the genus Hippocampus automatically assures that the seahorses sold at your LFS are cultured animals.

If the seahorses in question are over 4 inches in total length, there is a strong possibility the seahorses were harvested from the wild. It’s a mistake to assume that since CITES regulations to protect the genus Hippocampus went into effect last year that all the seahorses now being exported to the US have been captive-bred-and-raised. Plenty of wild-caught seahorses are still entering the country, destined for the pet trade.

The CITES regulations currently use a size limit to manage the seahorse fishery. Seahorses smaller than 10 cm or about 4 inches in length are illegal under CITES and cannot be imported or exported by member nations. However, wild-caught seahorses larger than 4 inches can still be imported legally if the necessary permits are obtained. Also, CITES regulates only the international trade in seahorses, so Hippocampus erectus and Hippocampus zosterae collected in US coastal waters are exempt from the regulations and can still be marketed freely within the US.

So when you purchase seahorses from your LFS there is a good possibility that they may have been procured from the wild or pen-raised rather than born and raised in captivity at an aquaculture facility. It’s fine if you want to give the new seahorses at your LFS a try, but because of the uncertainties surrounding them, be sure to play it safe and quarantine them before introducing them to your main tank, just as if they were wild seahorses. Assume they are wild or at best pen-raised and take all the necessary precautions so you won’t get burned. And I would also be a very sensible precaution to set up a new tank just for them, rather than mingling them with your existing captive bred livestock.

In general, if you’re new to seahorse keeping, you will increase your chances for success if you start off with hardy, easy to feed, captive-bred-and-raised livestock you obtained directly from a reputable breeder such as Ocean Rider.

Consider Ocean Rider’s strains of captive-bred-and-raised Hippocampus erectus, for example, Kaie. Ocean Rider has been working with this species intensively since 1998, and they have now been selectively bred for traits such as adaptability, disease resistance, vigor, aggressive feeding habits, and rapid growth for dozens and dozens of generations. Far from being recessive characteristics that could eventually result in inbreeding, these are all adaptive traits that increase the line’s fitness and improve survivorship. In fact, they are the same sort of traits Mother Nature herself selects seahorses for in the wild to assure survival of the fittest. When nature culls out the weakest and least fit, it is known as “natural selection.” It is nature’s way of keeping a species strong, vigorous, and adaptive (i.e., evolving to better fit its niche). The only difference is that Mother Nature is selecting for suitability to their natural habitat, whereas aquaculturists are selecting seahorses for fitness to captive conditions. In both cases, the selection process assures that the specimens become ever stronger and better adapted to their environmental niche, whether that is the aquarium or the ocean itself.

Practiced in this manner, selective breeding actually strengthens and improves a strain generation by generation, producing seahorses that are progressively hardier and better suited for aquarium life. This level of domestication not only improves their general health but also eliminates much of the stress wild seahorses experience in captivity, allowing cultured seahorses not only to live longer and healthier but to live better as well.

So Mustangs and Sunbursts (H. erectus) are now very hardy specimens that are supremely well adapted for aquarium life.

I will attach a document to this e-mail that explains all about Ocean Rider Mustangs and Sunbursts, including dozens of full-color photographs, so that you can download the document, save it on your computer, and then read through the information at your convenience, Kaie. You should have a much better idea of what the Sunbursts are really like in a home aquarium once you’ve had a chance to look through the document.

In addition, it would be a good idea for you to participate in the Ocean Rider seahorse training program considering the problems you’ve been having with your ponies lately. The Ocean Rider seahorse training manual is very comprehensive, consisting of several hundred pages of text with more than 250 full-color illustrations, and it will explain everything you need to know in order to keep Ocean Rider seahorses successfully in a home aquarium. We provide a free copy of the seahorse training manual to all first-time buyers and customers to assure that home hobbyists are well prepared to give their ponies the best possible care before they make a purchase.

All things considered, you may want to consider administering a regimen of fenbendazole (brand name Panacur) to eliminate any hydroids or Aiptasia that could possibly be stressing your seahorses. In the meantime, you may want to obtain a copy of the Ocean Rider Seahorse Training Manual to assure that you are providing your ponies with the best possible care. If so, just contact me via e-mail offlist, and I will send you your free copy of the training manual right away and do my best to answer any other questions you may have about the care and keeping your seahorses. You can always reach me at the following e-mail address:

[email protected]

Please let me know if I can be of any further service in the meantime, kaieocean.

Respectfully,
Pete Giwojna, Ocean Rider Tech Support