Re:baby seahorses!!!

Pete Giwojna

Dear hobbyist:

I am very sorry to hear about the increased mortality among your juvenile seahorses and the loss of the adult female.

It’s very difficult to say what may be wrong with so little to go on, but I would be happy to share my thoughts with you in that regard. The unusual symptoms (disorientation and a loss of motor skills and coordination) you describe may possibly be due to accidental poisoning or some other environmental disease.

Hobbyists sometimes see neurological symptoms like that under hypoxic conditions when seahorses have been deprived of oxygen for too long. However, it’s unlikely that your seahorses could be suffering neurological symptoms from a lack of oxygen due to hypoxic conditions without showing some signs of rapid breathing, and you didn’t mention any signs of respiratory distress in your message.

So it’s more likely that some sort of toxin or contaminant may have found its way into your aquarium accidentally. To investigate that possibility, let’s review some of the environmental diseases that can affect seahorses, including heavy metal poisoning, which can produce symptoms that are very similar to the behavior you describe:

Environmental Diseases Associated with Water Quality

Heavy metal poisoning is an environmental disease hobbyists must sometimes contend with. Even tiny concentrations of heavy metals are deadly to marine fish and invertebrates. This used to be a common cause for concern among marine aquarists when steel-framed aquariums were commonplace, but the advent of all-glass tanks and acrylic aquaria have greatly reduced such problems.

The chief offender nowadays is copper, which usually becomes a problem when the hobbyist overdoses the tank with a copper-based medication (Indiviglio, 2002). Other times copper enters the aquarium in tap water used for water changes or topping off the tank. The copper is leached into the tap water from copper pipes and plumbing (Indiviglio, 2002).

Other heavy metals (iron, lead, and aluminum) sometimes also present a problem when they are accidentally introduced to the aquarium in rocks, gravel, ornaments or decorations. Some of rocks and gravel sold (e.g., red flint) for freshwater use are unsafe in marine tanks because of a high metal content. The same is true for many aquarium ornaments and decorations (Giwojna, 1990). Be especially wary when purchasing artificial plastic plants for the aquarium. Stick with calcareous rocks and gravel and make certain any ornaments or plastic plants you consider are designed for use in marine aquariums and certified to be safe.

Even the popular sponge or foam filters are often a hazard. Many of them contain metal weights as ballast to hold them on the bottom, which is fine in freshwater but can be deadly in a saltwater setup when the metal slugs corrode and leach heavy metal ions into the water.

Seahorses suffering from heavy metal poisoning will act as if they are falling-down drunk. They will be listless and loggy, and if they attempt to move, they will be disoriented, bump blindly into things, and have great difficulty maintaining their normal equilibrium and balance (Giwojna, 1990). If they attempt to eat, they will be unable to target the food items properly and appear uncoordinated when they try to slurp up their prey. And as their condition worsens, they will begin breathing hard and fast.

Treatment is to get the seahorses into clean saltwater ASAP, identify the source of contamination and eliminate it, and change out the water in the main tank. Polyfilter pads pull out copper and many heavy metals and may be especially useful in such a situation.

Contamination of the aquarium water with household chemicals is another common problem for the hobbyist (Indiviglio, 2002). Avoid using anything that gives off strong fumes anywhere near your aquarium! This includes bleach, paint, lacquer, varnish, paint thinner, turpentine, insect sprays, bug bombs, pesticides, hairy spray, cigarette smoke, and household cleaners of all kinds (Giwojna, 1990). Even if the aquarium is tightly covered or sealed with plastic, airborne contaminants from fumes and aerosols will still be pumped into the aquarium from the air pumps (Indiviglio, 2002). To prevent this from happening when you must use such products near an aquarium that cannot be moved, disconnect the air pumps first and work only in well-ventilated area. Use submersible powerheads to maintain circulation in the covered aquarium, work fast, and air out the room thoroughly before you reconnect the air supply.

Medicating the aquarium is the worst possible thing you can do when seahorses are suffering from diseases related to water quality or environmental problems such as the toxic conditions described above (Giwojna, 1990). Afflictions such as these are not caused by parasites or pathogens, so medicating the tank not only fails to address the problem, it actually makes matters worse (Giwojna, 1990). Chemotherapeutic agents can be harsh on the seahorses, especially when they are already weakened due to poor water quality or actual poisoning. Worse yet, they are often hard on the biofilter as well and apt to further degrade water quality by killing off beneficial Nitrobacter and Nitrosomonas bacteria.

Therefore, when accidental poisoning may have occurred, a series of water changes combined with activated carbon filtration and the use of Poly-Filter pads is the best treatment option, and that’s what I would suggest in this case.

A water change and aquarium clean up is a good place to start whenever you suspect your seahorses may be having a problem. In most cases, the surest way to improve your water quality and correct the situation 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 source of the stress before your seahorses become seriously ill and require treatment.

In addition, I suggest that you drop the specific gravity in your aquarium down to 1.015 as soon as possible. Lowering the salinity in the aquarium can have a beneficial effect in situations like this for a number of reasons. For one thing, it will make it easier for the seahorses to osmoregulate, helping them to build up their strength.

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). Lowering the salinity as in the aquarium can therefore help ailing seahorses to maintain their energy reserves, giving them a better chance to recover.

Reducing the salinity also increases the amount of dissolved gases the aquarium water can hold. This helps protect against gas supersaturation and increases the levels of dissolved oxygen, helping the seahorses to breathe.

And reducing the specific gravity to 1.015 also protects the seahorses against many protozoan parasites and ectoparasites, which is another potential problem that hyposalinity can set right.

When the salinity in the aquarium is lowered, it is done as if performing a normal water change, except that the replacement water is simply treated tap or RO water without the salt (Don Carner, pers. com.). (If the replacement water is RO/DI or other softened source, then a buffering agent should be employed to prevent pH and alkalinity drops; Thiel, 2003.) Make sure the freshwater you add is thoroughly mixed with the remaining saltwater in the tank as you proceed. This will assure that your salinity/specific gravity readings are accurate. Monitor the lowering closely so as to not reduce it too fast. Achieving the desired specific gravity of 1.015 over a period of several hours is fine (Don Carner, pers. com.). The bacteria colony in the biofilter will not be adversely affected and the seahorses will handle the change in salinity without missing a beat. Any delicate invertebrates that may not tolerate a change in salinity should be removed for safekeeping before hand. (If you contact me off list at [email protected], I will provide you with a lot more information on the benefits of hyposalinity at how to administer it safely and easily.)

In summation, I would recommend performing one or more water changes in conjunction with a judicious aquarium cleaning, adding activated carbon and a polyfilter pad to your external filter to remove any possible toxins are contaminants that may have found their way into your seahorse setup, and reducing the specific gravity in the tank to 1.015 to help the seahorses recover.

I’ll do my best to answer your remaining questions one by one below:

1. i have not discovered any new babies since the originals over 3 months ago. is it likely that they are continuing to breed, but that it was just a fluke that i happened to see them the one time before they became lost?

Normally, a pregnant male will re-mate shortly after he delivers his latest brood, sometimes within an hour of ejecting the last of his young. In most cases, a mated pair of seahorses re-mates within 24-48 hours after the male gives birth.

So if you have not seen any further indications of breeding, or discovered any more newborns, I suspect that’s because your seahorses have not mated again, rather than because the babies are disappearing or being predated before you notice the big event.

Seahorses are most likely to give birth in the early morning hours shortly before or after sunrise, so if your not be an early riser, you may well have missed the spectacle of your male giving birth. For instance, this is how Carol Cozzi-Schmarr describes this phenomenon at the Ocean Rider aquaculture facility in Hawaii:

" Male seahorses can give birth any time of day or night. Usually it depends on the photoperiod in your tank and when they are most comfortable. In my experience, I have seen that 90% of the time the male seahorse will give birth right at the crack of dawn. For example, in one section of our hatchery we have over 50 pairs of seahorses. On any given morning if you show up just before dawn, you will witness at least 5 males giving birth at exactly the same time which is right at dawn. It is spectacular!! So, I would bet that if you set your alarm to 1 hour before sunrise you just might get lucky!! But of course, you will have to ask Mr. seahorse to be sure!!!
Aloha, Carol"

But even if you missed the big moment, it would be very difficult to overlook the aftermath. A new brood of pelagic Hippocampus erectus fry is normally discovered immediately upon arising in the morning in the form of a writhing mass of newborn seahorses, hopelessly tangled together at the top of the tank.

This dangerous situation develops because a newborn’s first instincts are to head to the surface to fill its air bladder and then to anchor itself to something solid. In the vastness of the ocean this is not a problem, since strong currents rapidly disperse the young, but in the confines of an aquarium, the first hitching post it finds will very likely be the tail or snout of one of its siblings. The same mistake is apt to be repeated by the rest of the pelagic fry, as they cluster at the surface, until the entire spawn is snarled together tail-to-tail, head-to-tail, tail-to-snout and so on. This is a very common experience when raising seahorses such as Hippocampus erectus, H. reidi, and H. ingens, which produce large broods of pelagic fry.

In short, if your seahorses were actively breeding, I think you would have detected the signs of pregnancy in the males as their brood pouches expanded to accommodate the developing young, and it would be equally hard to miss the swarm of pelagic young at the surface of the aquarium afterwards.

2. do you know how old the mustangs are typically when you guys sell them? how long do they usually live? when do they become full-sized? the babies i have now are not anywhere CLOSE to full grown.

Mustangs and Sunbursts (Hippocampus erectus) are usually shipped around the age of 5-7 months, which is about when they begin to hit sexual maturity and pair off with one another. They are usually about 4 inches in total length at this age. Although most individuals are sexually mature when they are shipped, they normally don’t reach their maximum growth (6+ inches) until they are yearlings (i.e., between 1-2 years of age).

In my experience, Mustangs and Sunbursts (Hippocampus erectus) have a life expectancy of 4-6 years in the home aquarium, if provided with good care. I have a pair of Mustangs in one of my home aquariums that are over five years in age, and I personally know of one old war horse raised by a colleague of mine 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, but of course the ideal conditions there are far different from the small,-closed-system aquaria and artificial saltwater we hobbyists must rely on.

3. my tank is completely overgrown with plants. it looks pretty, keeps the algae under control, and the seahorses seem to love having all the places to hide and hitch onto. i’ve always thought plants were great for an aquarium, but can you have too much of a good thing?

Seagrass meadows and algae beds are natural biotypes for seahorses, so a well-planted aquarium mimics their natural habitat for a well and often makes seahorses feel right at home. But there are a couple of circumstances under which an abundance of marine plants can become problematic in a small, close-system aquarium.

The first of these is is a sudden die off of a bed of Caulerpa due to stress or sexual reproduction. This can be harmful because toxins may be released by the Caulerpa in the die off and the resulting decay of a considerable quantity of vegetable matter can degrade the water quality and reduce the level of dissolved oxygen in the tank due to a bacterial bloom. In severe cases, this combination of events can stress the other aquarium inhabitants or even wipe out the entire tank.

For more information on this phenomenon, see Anthony Callo’s on the Best Plants and Algae for Refugia — Part II "Vegetable Filters," which is available online at the following URL:

But if the aquarium is well circulated, well aerated, and well filtered, even one of these dreaded vegetative events or Caulerpa die offs is more of a nuisance than a threat to the aquarium inhabitants.

As a case in point, consider the two-gallon tank I set up for photographic purposes when I did my first book on seahorses many years ago. This tank was lushly planted with an assortment of Caulerpa and other decorative macroalgae (Penicillus capitatus, Udotea, Halimeda sea cactus, etc.) and heavily stocked with a thriving colony of dwarf seahorses. Sure enough, right in the midst of a photo shoot, the Caulerpa chose that moment to die en masse, disintegrate and cloud the water. Much to my consternation, it turned the entire tank as opaque as a glass of milk in a matter of moments! At first visibility in the tank was perhaps an inch at best, but this gradually began to improve and after a period of several hours, the tank was crystal clear again. The primary source of filtration and aeration for that tiny tank was a simple, air-operated undergravel filter along with a considerable quantity of activated carbon, yet all of the dwarf seahorses survived the event with flying colors. In fact, one of the gravid males had given birth during the white out, and even the newborn fry were fine.

If you’re growing Caulerpa in your seahorse tank, jfarmer, it can easily be prevented from going sexual and dying of simply by aggressively thinning out the colony. This is accomplished by regularly plucking out excess fronds of the fast-growing Caulerpa; when you subsequently you remove the excess Caulerpa you’ve plucked out of the main colony, you’re exporting phosphates, nitrates and other nutrients from the tank, thereby helping to maintain good water quality, and pruning the runners helps keep it from going sexual.

When thinning out Caulerpa macroalgae, take care not to actually cut it. Remember, you’re not pruning hedges or trimming trees — the idea is to carefully pull up and remove continuous, unbroken fronds. Simply thin out the colony of excess strands, gently plucking up convenient fronds that can be readily removed intact. A little breakage is fine, but cutting or breaking too many strands will result in leaching undesirable substances into the aquarium water as the Caulerpa’s lifeblood drains away. Too much cutting or breaking can thus sap the colony’s strength and cause die offs or trigger the dreaded vegetative events that judicious thinning otherwise prevents.

If you’re concerned about your ability to maintain and control of Caulerpa properly, just use a different forms of macroalgae that grows less rapidly instead and you can get the same sort of benefits at relatively little risk.

The second situation in which a heavily planted aquarium can have an unintended impact on the marine aquarium is by altering the levels of oxygen and carbon dioxide in the aquarium as a result of photosynthesis. When the aquarium reflector is on, providing plenty of light, the algae and plants in the aquarium take in carbon dioxide and release oxygen as a byproduct of photosynthesis. As a result, the pH of the water and the dissolved oxygen levels rise throughout the day, while the level of dissolved carbon dioxide drops.

Due to this process, you may notice tiny bubbles forming on your macroalgae and plants during the day. Those bubbles are the oxygen that the plants release when they are photosynthesizing. That’s perfectly normal and the only way it might present a problem would be if the macroalgae in your heavily planted tank were producing so much oxygen during the day that the aquarium water became supersaturated with it. That’s very unlikely and you can easily check whether oxygen supersaturation is occurring by using an oxygen test kit, as explained later in this message.

On the other hand, during the night when the aquarium light is turned off and no photosynthesis takes place, the plants will begin to take in oxygen and give off carbon dioxide. This has exactly the opposite effect — the pH of the aquarium water and the level of dissolved oxygen drop at night, while the amount of dissolved carbon dioxide rises. This can occasionally become a problem in a small, poorly circulated, closed-system aquarium that is very heavily planted if the oxygen levels drop so much during the night and the carbon dioxide levels rise so high that the seahorses have difficulty breathing and getting enough oxygen.

Seahorse setups are often more susceptible to such problems because hobbyists are 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, aggravating the situation.

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, and in extreme cases, they can be asphyxiated overnight.

The daily fluctuations in pH, photosynthesis, dissolved oxygen/carbon dioxide, and redox levels that we have been discussing are natural and take place to a certain extent in all marine aquariums. Daily variances in chemical, physical and biological phenomena are a fact of life in aquaria, linked to the light and dark cycles and the diurnal rhythms of captive aquatic systems. As one example, the pH of aquarium water typically peaks after the lights have been on all day at a maximum of perhaps 8.4, only to drop to low of below 8.0 overnight. This is of course related to photosynthesis and the fact that zooanthellae and green plants consume CO2 and produce O2 when there is adequate light, but in essence reverse that process in the dark, consuming O2 and giving off CO2. Redox levels, available calcium and other water quality parameters are affected in similar ways. Ordinarily, these normal daily variations are not a cause for concern, but in a very heavily planted aquarium it’s possible, however unlikely, that they could result in oxygen supersaturation during the day or too little dissolved oxygen during the night to the detriment of your seahorses.

You can easily check if your well planted seahorse tank is at any risk from these processes simply by checking the dissolved oxygen levels at the end of the day right before you turn off the aquarium for the night, at which time the oxygen levels should be at their highest, and then re-checking the dissolved oxygen levels first thing in the morning before you turn the aquarium lights on, which is when the dissolved oxygen levels should be their lowest. Compare and contrast these two readings to see how much of a difference there is in the dissolved oxygen levels during the day and overnight. Compare the readings to the optimal level of dissolved oxygen — if the dissolved oxygen level is off the chart during the day, there could be a danger of gas supersaturation; on the other hand, if the dissolved oxygen level is dropping far below the optimal range overnight, there could be a danger of asphyxiation, particularly during summertime heat waves (the warmer the water, the less dissolved oxygen it can hold).

The Tetra Oxygen Test Kit (TetraTest 02) is a good liquid reagent test kit for fresh or saltwater with simple color scales for comparing readings that tests for 02 in the range of 2-14 PPM. It will cost you between $8.50 to $14 depending on where you shop and should be available at any well-stocked LFS. Salifert also makes a nice 02 Test Kit (their 02 Profi-Test) that will run you about $20.

Either of those test kits fit the bill very well and are worthwhile investments for the seahorse keeper.

Dissolved Oxygen (02): Optimum level = 6 – 7 ppm

High levels of dissolved oxygen are vital to the well being of both fish and invertebrates. The key to maintaining high O2 levels in the aquarium is good circulation combined with surface agitation (Webber, 2004). Wet/dry trickle filters, bio-wheels, and protein skimmers facilitate efficient gas exchange and oxygenation. It is important for the hobbyist to monitor the dissolved oxygen levels in the aquarium because a drop in O2 levels is often an early indicator of impending trouble — a precursor of problems ahead. A drop in O2 levels will tip off the alert aquarist and allow corrective measures to be taken, nipping the problem in the bud before it adversely affects his seahorses. For example, a drop in O2 levels could be an early indicator of overcrowding — a signal that your system has reached its carrying capacity. Or it may merely signal a rise in the water temperature due to a summertime heat wave or indicate that the tank is overdue for a water change and/or a thorough cleaning to remove excess organics and accumulated detritus. Or it could be telling you that your tank is under circulated and you need to increase the surface agitation and water movement.

The point is that checking the O2 levels in your aquarium can alert you to impending problems and allow you to do something about them before they have dire consequences. A drop in O2 levels is often the first sign of a water quality problem and it can tip off the alert aquarist that trouble is brewing before his seahorses are gasping for air in obvious respiratory distress. Checking the dissolved oxygen levels regularly is the next best thing to continuously monitoring the Oxidation-Reduction Potential (ORP) or redox of the water, which is a luxury few hobbyists can afford.

As long as your dissolved oxygen levels are in the normal range at the end of the day and overnight, and there are no vegetative events during which the macroalgae dies off en masse, then you can be confident that your well planted aquarium isn’t creating any problems for your seahorses. Reducing the specific gravity in your aquarium to 1.015 will increase the amount of dissolved oxygen the water can hold, and therefore guard against both gas supersaturation and asphyxiation.

Best of luck getting your seahorse system back to normal. Here’s hoping the two surviving three-month juveniles continue to grow and thrive.

Pete Giwojna

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