Re:Cindy not acting right

Pete Giwojna

Dear Denise:

I am sorry to hear that Cindy is having some problems recently, Denise. I have examined the photographs that you send me off list and I don’t see anything that suggests an obvious health problem. Her eyes are clear and I don’t see any ulcerations or open sores or suspicious areas that could indicate a possible skin infection. Nor can I see any indications of snout rot their tail rot on any of the photographs. She has darkened in coloration in comparison to other photos of Cindy I have seen, which could be an indication that something is stressing her, and the abnormal behaviors you noticed also suggest that something is bothering her. But there is nothing I can clearly diagnose from the photographs in this case…

Hanging out near the bottom of the tank rather than venturing up toward the surface as usual, and not holding yourself and usual upright position when perched on her favorite hitching posts, but rather laying horizontally with her head almost touching the bottom, are indications of a seahorse that is experiencing negative buoyancy (i.e., the tendency to sink). But there are number of different things that may contribute to, or cause a seahorse to develop problems with negative buoyancy, so I am uncertain as to what may be the best way to proceed under the circumstances, Denise.

For instance, negative buoyancy is sometimes 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 could 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, Denise, and I will provide you with a treatment regimen that should be helpful.)

But laying prone with your head almost touching the bottom of the tank for extended periods, rather than holding herself upright, could also be an indication of generalized weakness, Denise. 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 transitory 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.)

Finally, Denise, in seahorses, many times a problem with negative buoyancy is simply the result of an underinflated gas bladder or swimbladder, which the seahorses may even eventually correct on their own, as explained in more detail below:

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 (Seahorse Anatomy, 2004). 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 well down into the body cavity along the dorsal boundary (Seahorse Anatomy, 2004). It will have a whitish to silvery appearance and is a simple, single-chambered sac that begins at the bend in the neck and extends to about 1/3 of the length of the coelomic cavity (Bull and Mitchell, 2002).

The gas bladder arises as a simple pouch or outgrowth from the foregut (Evans, 1998). In newborn seahorses, this connection with the gut is retained as an open tube, called the pneumatic duct, and seahorse fry gulp air at the surface to fill their gas bladder initially. There is only a short window of opportunity to do this, since the fry lose this open connection very early in life. As a result, the air bladder is often completely closed off (physoclistous) in fry that are more than a few days old, and they can no longer inflate their gas bladders this way. Consequently, fry that miss this early opportunity to gulp air — perhaps as the result of an oily or greasy film at the surface of the water — suffer from underdeveloped swim bladders. As they grow and become heavier, they sink to the bottom and are unable to swim or feed normally. On the other hand, accidentally ingesting air after the pneumatic duct closes off, or over inflating the swim bladder by gulping too much air while feeding at the top or entrapped by the surface tension, result in fatal buoyancy problems that leave them bobbing helplessly at the surface, again unable to feed.

Past the newborn stage, the seahorse’s swim bladder is completely self-contained, with no duct connecting it to the esophagus. As a result, they can only regulate their buoyancy by resorbing gas from the swim bladder or secreting more gas into the bladder, which is a relatively slow process (Jobling, 1995).

The composition of the gas contained within the swim bladder is about 80% oxygen, with much lesser amounts of carbon dioxide and nitrogen (Evans, 1998). The oxygen that fills the swim bladder is delivered via the bloodstream, but in order to do this, the oxygen must be secreted from the blood to the lumen of the swim bladder against a strong gas pressure gradient, and once deposited therein, the gas must be prevented from diffusing back into the blood (Evans, 1998).

This is accomplished with the aid of the gas gland, a very sophisticated organ located in the wall of the swim bladder, and the rete mirable or “miraculous net,” which delivers blood to the gas gland (Evans, 1998; Jobling, 1995). With the help of the rete mirable, the gas gland is capable of extracting gases from the blood stream and concentrating them into the swim bladder. The rete mirable is basically a dense network of blood vessels running parallel to each other, which function as a countercurrent exchanger. Capillaries carrying oxygen-rich arterial blood from the gills to the gas gland run parallel to and directly alongside capillaries carrying oxygen depleted venous blood from the gland in the opposite direction (Evans, 1998). It is countercurrent exchange in the rete mirable that acts to retain the swim bladder gases. To the naked eye, the rete mirable appears as one or more circular patches of blood vessels on the surface of the swim bladder (Diseases of Ornamental Fish, 2004).

Gasses and solutes in the venous blood leaving the gas gland move into the incoming arterial blood through the rete mirable via passive diffusion and are returned to the gas gland (Evans, 1998). In this way, the rete acts as a trap that retains the gases in the swim bladder.

The respiration of epithelial cells in the gas gland releases lactic acid and CO2, and these substances are then trapped in the rete via countercurrent exchange and returned to the gas gland where they accumulate (Evans, 1998). As a result of this multiplying effect of the rete mirable, conditions within the gas gland can become 10 times more acidic than normal (Evans, 1998). This is important because hemoglobin loses the ability to bind oxygen under acidic conditions, so the oxygen-rich arterial blood flowing into the gas gland releases the oxygen it is carrying in the gland (Evans, 1998). The oxygen that’s offloaded due to the acidification of the blood becomes concentrated in the gas gland until it is finally secreted into the swim bladder itself.

Removing excess gas from the swim bladder is an entirely different matter. The gas gland plays no role in gas resorption, which occurs in an entirely different area of the swim bladder, called the oval (Evans, 1998). The surface of the swim bladder in the oval region is covered with a meshwork of thin blood vessels, which receive a different blood supply altogether than that of the gas gland (Jobling, 1995). It is there, in the oval, that gas resorption occurs. Gas removal takes place only when a fish is rising in the water column and thus experiences reduced hydrostatic pressure. At other times, the blood vessels that supply the oval are closed off by a series of muscular valves; with no significant blood flow to the oval, there can be no gas resorption (Evans, 1998).

Okay, Denise, that’s a quick rundown on how the seahorse’s gas bladder or swimbladder regulates its buoyancy. The mechanisms described above allow the seahorse to maintain neutral buoyancy, the point at which is weightless in the water, and can therefore maneuver and swim about effortlessly. Many times when a seahorse is experiencing a problem with negative buoyancy, it will be able to resolve the problem itself by secreting more oxygen from the gas gland into the swimbladder. But this is a slow, gradual process that may take several days. As long as the seahorse is still eating and keeping up its strength, you can afford to wait a few more days to see if the problem corrects itself.

Under the circumstances, Denise, I would suggest that you go ahead and perform your partial water change as usual in order to make sure that the ammonia and nitrite levels remain at zero and to reduce the nitrate levels as much as possible. At the same time, try to increase the surface agitation in the main tank and increase the aeration is much as possible in order to promote better oxygenation and to facilitate efficient gas exchange at the air/water interface. This will assure that the levels of dissolved oxygen remain nice and high, while the levels of dissolved carbon dioxide are nice and low. Go ahead and add an extra airstone or two, if necessary. That will make it easier for the seahorses to breathe as well as stabilizing the pH in the desired range, and you may notice that the seahorses have more energy and an increase in appetite as a result.

At the same time, you might also want to consider obtaining some choice live foods to tempt Cindy to eat more and help her to keep her strength up. Any kind of suitable living prey will do nicely for this purpose, Denise: Mysids, feeder shrimp, Gammarus or adult Artemia — the type of food isn’t really as important as the fact that it’s alive and kicking. Nothing stimulates a sea horse’s feeding instincts like the frantic movements and evasive maneuvers of real, live, "catch-me-if-you-can" prey items (Giwojna, 1996).

That’s why I like to use occasional treats of live food as behavioral enrichment for my seahorses. They get the thrill of hunting after and chasing down live prey, which livens things up for them in more of ways than one and is a nice change of pace from their daily routine in captivity. Live foods are guaranteed to perk up an ailing appetite and excite the interest of the most jaded "galloping gourmets."

I also find live foods to be especially useful for those rare occasions when seahorses are ailing and must be treated. Many medications (e.g., Diamox) have the unfortunate side effect of suppressing appetite, so when treating sickly seahorses, it’s a good idea to tempt them with choice live foods in order to keep them eating and help build up their strength while recuperating. Separating an ailing seahorse from its mate and herdmates and transferring it to a strange new environment for treatment can be a traumatic experience, especially since the Spartan surroundings in the sterile environment of a sparsely furnished hospital tank can leave a seahorses feeling vulnerable and exposed. Live foods can counteract these negative affects to a certain degree, and offer a little excitement that distracts the isolated seahorse temporarily at least from its melancholy.

Some of the choice live foods that seahorses find irresistible are Ocean Rider’s red feeder shrimp (Red Iron Horse Feed, Halocaridina rubra), Gammarus amphipods, and the live Mysis post-larval Feeder Shrimp from Drs. Foster and Smith ( These live bite-size crustaceans are what I’d like to call a "feed-and-forget" food. They are tough, rugged little shrimp that you can toss in your tank with no acclimation whatsoever. They are agile and elusive enough that your filters won’t eat them and the seahorses won’t be able to capture them all right away. Some will hide and evade well enough that your seahorses will still be hunting down the stragglers for the next day or two. Best of all, you can toss a nice batch of them in your aquarium, secure in the knowledge that they won’t perish and pollute it, but thrive and survive as real, live, "catch-me-if-you-can" prey items that seahorses cannot resist.

The Ocean Rider Aquaculture Facility in Hawaii ( is a good source for the following live foods:

Green Iron Horse Feed (Gammarus amphipods)
Red Iron Horse Feed or Volcano Shrimp (Halocaridina rubra)

Or the live Mysis or post-larval Feeder Shrimp from Drs. Foster and Smith would also be a good choice for this. You can obtain 100 live Mysidopsis bahia for $33.99 or 100 bite-size Feeder Shrimp for $39.99 from and your seahorses will love them. Just copy the following URL (everything within the angle brackets below), paste it in your web browser, and press the "Entered" key, Denise, and it will take you directly to the right webpage:


Some hobbyists have good success coaxing a finicky seahorse to feed by transferring the seahorse to a critter keeper or breeder net or similar enclosure that can hang within the main tank itself, and then adding a generous portion of live feeder shrimp to the container. Within the enclosure, the affected seahorse does not have to compete with its tankmates for the live food, and it is easy to maintain an adequate feeding density within the confined space so that there is always a bite-size feeder shrimp passing within striking distance of the hungry seahorse. If the affected seahorse is still interested in feeding at all, then releasing it in an in-tank enclosure like this where it will be surrounded by plenty of tempting live feeder shrimp and can feed at its leisure may help it to keep its strength up and recover more quickly. Add one or two hitching posts within the critter keeper or breeder net so that the seahorse can anchor in place and wait for a tasty shrimp to pass within easy reach, and give him an hour or two within the enclosure to eat his fill of the feeder shrimp. You can monitor his progress from a nonthreatening distance away from the tank to see how he is doing. In most cases, the seahorse quickly becomes familiar with the routine of being transferred to the special enclosure at feeding time and associates it with tasty live foods and a full belly — positive reinforcements that make it a very nonthreatening, stress-free procedure for the affected seahorse — and, as a result, it may actually come to look forward to it after a few feedings. You can repeat this feeding process two or three times daily in order to fatten him up again, if your schedule allows.

Performing a partial water change to make sure the water quality is up to snuff, increasing the surface agitation and aeration to raise the dissolved oxygen levels and reduce the levels of dissolved CO2, and keeping the seahorse eating by tempting it with choice live foods are some of the things you can do to improve Cindy’ situation while you are waiting to see if she is able to recover from the negative buoyancy on her own.

If Cindy is not able to recover on her own, it’s possible that an infection of some sort is interfering with the gas gland, or that she is suffering from a fluid buildup within her abdominal cavity (e.g., ascites), which would then indicate the need for medicating the seahorse in a hospital tank. Medications that combine trimethoprim with sulfa drugs are usually a good choice for such a problem.

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, Denise. If there is any doubt about your water quality, Don’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.

If you are going to be waiting to see if the problem resolves itself, it would be a good idea for you to obtain a medication that combines trimethoprim with sulfa drugs in the meantime, so you will have the appropriate medication on hand if the problem with neutral buoyancy does not correct itself. In that event, Denise, the medications that I prefer are either Sulfa 4 TMP Powder or TMP Sulfa, both of which can be obtained online without prescription from National Fish Pharmaceuticals.

Sulfa 4 TMP Powder

USE: this is a special blend of four different sulfas that all have different absorption rates and solubility. The sulfas are combined with trimethoprim, which potentiates each other’s ability to kill bacteria. The result is a wide spectrum antibiotic with less chance of resistant strains developing.

DOSAGE: 1/4 teaspoon per 20 gallons of water. (1/2 pound treats 3640 gallons of water.)
25 grams for $15.28

TMP Sulfa (trimethoprim and sulfathiazole sodium)

USE: for treating bacterial infections, both gram-negative and gram-positive. The combination of trimethoprim plus sulfathiazole sodium retards resistant strains from developing. It exerts its antimicrobial effect by blocking 2 consecutive steps in the biosynthesis of the nucleic acids and proteins essential to many bacteria.

DOSAGE: add 1/4 teaspoon per 10 gallons of water every 24 hours, with a 25% water change before each daily treatment. Treat for a minimum of 10 days.

(1/4 pound treats approximately 940 gallons of water.)
*More effective than triple sulfa.
25 grams for $$15.25

You can get both Sulfa 4 TMP Powder and TMP Sulfa from National Fish Pharmaceuticals at the following URL:

Best of luck restoring your female seahorse to normal again, Denise.

Pete Giwojna, Ocean Rider Training Tech Support

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