All my condolences on the loss of your female! It’s very difficult to determine what might have happened to her with so little to go on, but I would be happy to share my thoughts on the matter with you for whatever it’s worth.
Sherry makes a good point about the age of the seahorse. It is becoming more and more common for hardy domesticated seahorses to die of natural causes at a ripe old age. I know of a number of hobbyists who have been able to keep cultured seahorses to the end of their natural life span.
But I don’t think this is a case where the female died of old age. Ocean Rider typically ships out medium Mustangs and Sunbursts (Hippocampus erectus) at a size of about 4 inches when they are about 5-8 months of age. So if the female was purchased about one year ago, that means it was probably around 16-18 months old when it died.
In my experience, Mustangs and Sunburst (H. erectus) have a life expectancy of about 4-6 years in the home aquarium, if provided with good care. (I personally know of one old war horse that reached the ripe old age of 7 years and 3 months.) At the Ocean Rider facility, I believe some of their original broodstock are older still (8-10 years old), but of course the ideal conditions there are far different from the small,-closed-system aquaria and artificial saltwater we hobbyists must rely on.
Interestingly, if provided with optimal water quality, a nutritious diet, and favorable conditions, the old warhorses will often continue to breed successfully despite their age. Many times pairs produce their biggest broods between the ages of 3-5. Their frequency of breeding may go down, however, and they may produce fewer broods each season as they age. So I suspect this particular female likely had a couple of good years left in her had her life not been cut short unexpectedly. But it’s very difficult to say why she may have died prematurely…
I have seen one or two cases over the years in which healthy seahorses choked to death after accidentally ingesting a foreign object while feeding from the bottom. When this happens, a foreign object of some sort apparently lodges within the tubular snout, disrupting the flow of water over the seahorse’s gills so that it suffocates in a matter of moments. (It appears that the seahorse’s powerful suctorial feeding mechanism is much better at sucking objects into its tube mouth than it is at expelling something it has accidentally snicked up.)
If an episode like this takes place when the aquarist isn’t around to witness the event, he will return to discover to his or her dismay that a perfectly healthy seahorse is now lying dead on the bottom of the tank for no apparent reason. Choking or suffocating on a foreign object this way is an extremely unusual occurrence — as I said, I have heard of only a couple of such instances in all my years — but it is one more reason to train your seahorses to eat from a feeding trough of a some sort rather than slurping up frozen Mysis from the sand or gravel.
Mysterious deaths from asphyxiation can also occur in seahorses for reasons other than choking. For instance, hypoxia due to low oxygen levels or high carbon dioxide levels has been known to kill seahorses suddenly and without warning. This often tends to happen overnight when dissolved CO2 naturally rises as the O2 levels are dropping due to the reversal of photosynthesis.
As you know, while they are photosynthesizing during the day, zoanthellae and algae consume CO2 and produce O2, but at night, in the absence of light, this process is reversed and the photosynthetic organisms consume O2 and give off CO2 instead. Seahorse setups in general are susceptible to such problems because hobbyists are often so conscious of their seahorses’ limited swimming ability that they tend to leave their aquariums undercirculated. Poor circulation and inadequate surface agitation can lead to inefficient oxygenation and insufficient offgassing of carbon dioxide.
Seahorses are more vulnerable to low O2/high CO2 levels than most fishes because of their primitive gills. Unlike most teleost (bony) fishes, which have their gills arranged in sheaves like the pages of a book, seahorses have rudimentary gill arches with small powder-puff type gill filaments. Seahorses are said to have "tufted" gills because they appear to be hemispherical clumps of tissue on stems. Their unique, lobed gill filaments (lophobranchs) are arranged in grape-like clusters and have fewer lamellae than other teleost fishes. Because of the difference in the structure and efficiency of their gills, seahorse are unsually vulnernable to hypoxia when CO2 levels are high and/or O2 levels are low.
Most deaths due to hypoxia occur when the water pump or filter fails during the night, or there is a power outage overnight when the aquarist is unaware, cutting off the filtration, water circulation, and aeration of the aquarium with devastating results. But there are also a number of other factors that affect the levels of dissolved oxygen in the aquarium, and asphyxiation in seahorses can also occur when there has been no equipment failure.
For instance, heat stress due to a summertime heat wave can rapidly deplete the oxygen levels in a poorly circulated seahorse tank. It’s important to remember that the warmer the water, the less dissolved oxygen it can hold. Elevated water temperatures increase the metabolism of your seahorses, and therefore their consumption of oxygen, at the same time that the rise in temperature is reducing the amount of dissolved oxygen in the water. That creates a dangerous situation for seahorses and may well result in respiratory distress and rapid, labored breathing, as well as contributing to asphyxia under certain circumstances.
There is also an inverse relationship between salinity and dissolved oxygen. The higher the specific gravity or salinity, the less dissolved oxygen the water can hold. By the same token, the lower the salinity or specific gravity, the more dissolved oxygen the water can hold. Sometimes the specific gravity in a seahorse tank can creep up unbeknownst to the aquarist due to evaporation of the aquarium water, and the higher the specific gravity gets, the lower the dissolved oxygen levels in the aquarium will be.
A combination of these factors can be downright deadly. If a heavily planted tank is running too warm and if the specific gravity or salinity of the aquarium has risen higher than the suggested range (1.024-1.025), and the tank is undercirculated, that can sometimes be a recipe for disaster. The oxygen levels in the aquarium will be reduced as a result, and when the lights go off and photosynthesis ceases in a heavily planted aquarium, the oxygen levels will be further depleted while the CO2 levels are rising. In some cases, this can wipe out a tank full of healthy seahorses literally overnight, particularly if the tank is well stocked and houses several seahorses.
Such potential problems with hypoxia are sometimes exacerbated by a transient ammonia or nitrite spike following a heavy feeding. Such spikes are often difficult to detect with test kits because they normally clear up within several hours following the feeding. But despite their transitory nature, they may already have done their damage in the interim by affecting the seahorse’s blood and making it difficult for them to get enough oxygen. This happens because some of the hemoglobin in the red blood cells of the seahorse is converted to methhemoglobin when it is exposed to nitrogenous wastes such as the nitrite and ammonia, and methhemoglobin cannot transport oxygen. So if there is a spike in the nitrate or ammonia levels in your aquarium following a heavy feeding, impairing the ability of the seahorses to transport oxygen through their bloodstreams, at the same time that the dissolved oxygen levels are falling and CO2 levels are rising due to the sort of factors mentioned above, seahorses are in danger of asphyxiation.
In short, flyinglantis, if your water temperature is running on the high side, your seahorse system is undercirculated or overstocked, or the salinity has crept up higher than normal and/or there may have been an ammonia or nitrite spike following the last feeding of the day, it’s possible that your female could have asphyxiated overnight. But I don’t believe that’s a strong possibility, since you mentioned that your aquarium parameters are all right where they should be and none of the other seahorses in the tank were affected. When there is a lack of oxygen in the aquarium water, you can expect all of his seahorses to be affected to one degree or another, and if none of the other seahorses was showing any indications of respiratory distress or struggling for air (huffing, rapid respirations or labored breathing, blanching or unusual pallor) that fateful morning, then we can probably rule out asphyxiation.
Even so, it may be a wise precaution for you to increase the surface agitation and circulation in your seahorse tank to promote more efficient oxygenation. Consider adding an extra airstone or two anchored just beneath the surface of the tank to increase the aeration and facilitate better gas exchange at the air/water interface. Maintain stable water temperatures in the 72°F- 75°F range at all times and consider reducing the specific gravity of your aquarium to around 1.022 just in case. These measures will all help to increase the dissolved oxygen levels in the aquarium and prevent any problems with asphyxiation.
And, if you should ever find yourself dealing with such a situation in the future, remember that good old methylene blue can work wonders in cases of hypoxia and respiratory distress. Mommonly 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 ever need to treat with methylene blue:
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
If you obtained a brand of methylene blue other than Kordon, just follow the instructions the medication comes with. Remember that methylene blue will destroy the beneficial nitrifying bacteria in your biofilter, so it should only be administered in a hospital tank or a separate dipping container.
One other possibility we must consider, flyinglantis, is that an acute illness may have killed your female. That is also quite uncommon, particularly with hardy captive-bred-and-raised seahorses such as Ocean Riders. But on rare occasions it does happen when a peracute/acute illness involves the seahorse’s respiratory system or an infection become systemic. Such unusual events can kill a seahorse literally overnight without any premonitory signs. Hobbyists usually refer to this phenomenon as "Sudden Death Syndrome," although in most cases the unfortunate seahorse has actually been ill for quite some time before its demise. Its death seems sudden because the infection had been spreading internally, or the parasites had been spreading within its opercular cavities, with no outward obvious symptoms.
For example, acute or peracute infections of a protozoan parasite (e.g., Uronema species) can sometimes cause sudden death in seahorses. Gill flukes and gill parasites such as these can be difficult to detect at first in seahorses because their gills are covered by the opercula with only a small pore or opening that acts as an exhaust port for the water that is pumped over the gills. The numbers of these parasites can build up quickly within the seahorse’s enclosed gill chambers and cause death by smothering with little outward signs of a problem. But in the case of gill parasites, the infestation typically causes respiratory distress, panting, huffing, etc., and you reported no such breathing difficulties. And if gill parasites had smothered your female, they would also have affected the rest of your herd by now and the remaining seahorses would be exhibiting symptoms of respiratory distress. But that hasn’t happened. And, just as you said, it’s difficult to imagine how such parasites may have entered your aquarium, since the only inhabitants are the Ocean Rider seahorses and your cleanup crew. So I’m confident that we can rule out an acute or peracute Uronema infection or a problem with gill flukes or gill parasites. That makes me think that bacterial septicemia is more likely to have been involved, but that’s pure guesswork and speculation on my part.
An acute or peracute bacterial infection of some sort is the most common cause of SDS. When septacemia results from such infections, they can kill quickly with no apparent symptoms or signs of trouble. Outwardly, the seahorse seems to be fine, but all the while the infection is spreading internally, hidden and deadly. When such infections take hold in the bloodstream and become septic, they can cause death within a matter of hours.
As you know, your Ocean Rider seahorses were born and raised at a High-Health aquaculture facility and were therefore guaranteed to be free of pathogens and parasites when they were delivered to you. So your seahorses have not been harboring any disease organisms all this while like a ticking time bomb, nor is your cleanup crew likely to have introduced any harmful bacteria. But there are other ways for the seahorses to be exposed.
One of the most common ways this happens in the aquarium is by eating contaminated food. When feeding seahorses in a small, closed-system aquarium, the worst thing you can do is to scatter a handful of frozen Mysis throughout the tank to be dispersed by the currents and hope that the hungry horses can track it all down. Inevitably some of the frozen food will be swept away and lodge in isolated nooks and crannies where the seahorses cannot get it. There it will begin to decompose and degrade the water quality, which is why ammonia spikes are common after a heavy feeding. Or it may be wafted out into the open again later on and eaten after it has begun to spoil. Either outcome can lead to dire problems.
Or the frozen Mysis can pick up harmful bacteria via fecal exposure after laying on a dirty substrate before it was eaten. Our pampered ponies are particularly susceptible to problems from contaminated food because of the reduced immune system in the gut of the seahorse (Paul Anderson, pers. com.). Immunologists have found a reduction of Gut Associated Lymphoid Tissue (GALT) in the digestive tract of seahorses as compared to other fish such as the common carp, which habitually feed on the bottom muck in lakes and rivers. (GALT in the intestinal mucosa produces lymphocytes or white blood cells that help protect the body against bacteria and other foreign invaders.) The researchers hypothesized that the amount of gut associated lymphoid tissue has been evolutionarily reduced in syngnathids because their small snouts and habit of feeding on prey items from the water column or vegetation means they take in less pathogens when feeding than fish such as sea bass or groupers that have an enormous gape, or bottom feeders such as carp that are always rooting around in the muck (Paul Anderson, pers. com.). As a result, seahorses may have more difficulty inactivating or fighting off bacteria in their gut from tainted food. The substrate in a small, close system aquarium becomes loaded with bacteria over time, and internal parasites such as intestinal flagellates are transmitted through fecal contamination.
So you don’t want to broadcast feed or scatter feed the frozen Mysis to your seahorses. And you don’t want the ponies to be eating the frozen Mysis from the bottom of the tank if you can possibly avoid it. That’s unnatural and unhealthy for seahorses. Their tubular snouts are adapted for slurping up small crustaceans from the water column or plucking them out of dense vegetation, not for feeding off the sand substrate or gravel bed. Many cases of snout rot in seahorses can be traced to feeding off a dirty substrate.
The best way to avoid such problems is to set up a feeding station for your seahorses, so one other suggestion would be to train your seahorses to eat from a feeding trough, if you have not already done so. A feeding station is very simple concept. In essence, it is a simple feeding tray that will safely contain the frozen Mysis while your seahorses dine on it. The feeding trough thus prevents the food from being wafted away by currents or stolen by bottom feeders before the seahorses can slurp it up, and it makes cleaning up a snap.
Seahorses respond very well when they are fed at the same time and place each day. They quickly learn the routine and will come to recognize their keeper as the one who feeds them — the giver of gourmet delights! Once that happens, they will often beat you to the spot, gathering around their feeding station as soon as they see you approach.
For best results, I recommend elevating the feeding station, which provides several benefits for our galloping gourmets:
(1) First and foremost, it isolates the feeding trough from the bacteria-laden substrate and provides the seahorses with a sanitary lunch counter from which to feed.
(2) Secondly, it keeps the feeding station beyond the reach of bottom scavengers such as bristleworms, Nassarius snails and hermit crabs, which are attracted to the frozen Mysis.
(3) Finally, it provides a sterile feeding surface for the ponies that is easy to remove and keep clean, thereby making it a breeze to dispose of leftovers, which safeguards your water quality. Keeping the feeding tray elevated makes it convenient to clean and sterilize between feedings.
Once your seahorses have adjusted to their new home and are eating well, you will find that it’s fun and easy to train them to take frozen Mysis from a feeding station. I wrote an article in Conscientious Aquarist that explains everything there is to know about setting up a feeding station and teaching your seahorses to use it. It’s available online at the following URL:
Click here: Seahorse Feeders
All kinds of different objects will make a suitable feeding post or feeding trough. The following link will take you to a site with photographs of different types of feeding stations that seahorse keepers have devised to give you a better idea of the possibilities:
You can also buy ready-made feeding stations if you feel that would be easier than improvising one of your own. For example, the Aquarium Fish Dish sold here works well in some seahorse tanks:
Or you could try the following feeder that was designed specifically for seahorses:
Because the numbers of dangerous bacteria build up and accumulate in the aquarium substrate over time, it may also be a worthwhile precaution to perform a water change and judicious aquarium cleaning just on general principles, flyinglantis. In most cases, the surest way to improve the water quality and maintain optimum water chemistry is to combine a 25%-50% water change with a thorough aquarium clean up. Siphon around the base of your rockwork and decorations, vacuum the top 1/2 inch of the sand or gravel, rinse or replace your prefilter, and administer a general system cleaning. The idea is to remove any accumulated excess organic material in the sand/gravel bed, top of the filter, or tank that could degrade your water quality, serve as a breeding ground for bacteria or a reservoir for disease, or otherwise be stressing your seahorses. [Note: when cleaning the filter and vacuuming the substrate, your goal is to remove excess organic wastes WITHOUT disturbing the balance of the nitrifying bacteria. Do not dismantle the entire filter, overhaul your entire filter system in one fell swoop, or clean your primary filtration system too zealously or you may impair your biological filtration.]
At first glance your aquarium parameters may look great, but there are some water quality issues that are difficult to detect with standard tests, such as a decrease in dissolved 02, transitory ammonia/nitrite spikes following a heavy feeding, pH drift, or the gradual accumulation of detritus. A water change and cleanup is a simple preventative measure that can help defuse those kinds of hidden factors before they become a problem and stress out your seahorses. These simple measures may restore your water quality and correct the situation so there is no recurrence of any such problems in the future.
Best of luck with your remaining seahorses, flyinglantis!