Reply To: A Few Questions

Pete Giwojna

Dear Kayle:

I would be very happy to help you out with your new seahorse project, and I’ll do my best to answer your initial questions one by one below:

1. Is a tank height of 18 inches too low? I currently have a 24x24x18 tank I would like to use. I seem to get mixed opinions on this, and figured who better to ask then the people who actually bred the seahorses I want to get. Some say they have kept happy seahorses that bred in a tank only 16 inches high, and others say don’t go less than 24 inches.

I prefer taller tanks for seahorses for a couple of reasons, Kayle. In general, an aquarium at least 20-inches high is desirable (but not mandatory) when keeping the greater seahorses. They need the vertical swimming space to perform their complex mating ritual and successfully complete the egg transfer, which is accomplished while the pair is rising through the water column or drifting slowly downwards from the apex of their rise. If the aquarium is too shallow, eggs will be spilled during the transfer from the female to the male’s brood pouch, and mating becomes increasingly difficult or impossible below a certain minimum depth. A tall aquarium can also help protect the seahorses from depth-related health problems such as bloated pouch and certain forms of Gas Bubble Disease.

But an aquarium of 18 inches tall can certainly make a suitable seahorse habitat as long as you provide optimum water quality at all times and provide your ponies with good care.

2. I would like to keep some seahorse safe corals (gorgonians, zoas, mushrooms, and things of that nature that don’t sting. And nothing that needs intense light, as I read the ponies don’t like extremely bright light. Do you think the Blastomussa or Acanthastrea coral would fall under the safe category and not harm/sting them?

In general, seahorses do well with virtually all of the soft corals, Kayle. But you have to be more careful with the hard or stony corals since many of them have nematocysts that can produce painful stings to seahorses. The STS stony corals are much safer in that regard than the LPS stony corals.

For example, this is what I typically advise home hobbyists who want to keep seahorses in a modified reef systems with suitable live corals, Kayle:

<Open quote>
Live corals are a different matter altogether, and you must observe some special precautions when selecting corals for a seahorse tank. Here are some suggestions regarding what specimens do well with seahorses and which should be avoided, if you will be keeping live corals with your ponies or maintaining a reef biotype for them:

Seahorse-Proofing the Reef Tank

When designing a reef tank that will include seahorses, one must anticipate the different ways they might be injured in such a setup and then take precautions to prevent them from coming to harm. The process of rendering your reef system seahorse safe is much like the measures new parents take to childproof their house when they are expecting their first child. Intake tubes for the filters should be shielded, siphon tubes should be equipped with filter baskets or screens, and so on…

For instance, when powerful water movement is combined with overflows, there is a risk that seahorses could become pinned against an overflow or even go over it (Delbeek, Oct. 2001). Therefore, in the seahorse reef, overflows must be baffled and/or screened off, or the water flow should be adjusted sufficiently to prevent that from happening.

Likewise, although seahorses have no problem with strong currents in the wild, in the confines of aquarium, it is possible for them to come in contact with stinging corals if they are struck by a sudden powerful wave or surge, or are overwhelmed by a strong, unexpected current (Delbeek, Oct. 2001). The hobbyist needs to take this into consideration when placing water returns and corals in the seahorse reef (Delbeek, Oct. 2001). If possible, keep the water currents steady and unvarying so the seahorses can establish holding areas in the sheltered spots and low flow zones without getting blindsided by unpredictable currents.

One good way to accommodate both the needs of corals that prefer brisk currents and the seahorse’s need for slack-water retreats is to create tall rock formations a foot or two down current from the strongest water flows to intercept and deflect or divert that strong flow of water, creating eddies and slack-water zones where there is relatively little water movement down current. Seahorses will hold in these low flow areas when they want to move away from the current, so it’s a good idea to position convenient hitching posts in the lee or down-current side of such formations.

Another excellent way to accomplish the same thing is to use small powerheads to create and direct current wherever needed. A properly positioned powerhead can thus bathe your prized Acropora formations in a brisk water stream precisely without generating too much water movement elsewhere in the aquarium. Just be aware that powerheads can become death traps for seahorses if their intakes are not properly shielded or screened off, and take the necessary precautions (Delbeek, Oct. 2001). Carefully conceal the intakes amidst the rockwork where they will be completely inaccessible to seahorses, otherwise shield them, or screen them off with a sponge prefilter.

In short, the hobbyist who wants to keep seahorses in a reef system must be willing to make some concessions and modifications to accommodate their special needs nonetheless. For example, the reef keeper must be willing to limit himself to corals and invertebrates that meet the following criteria:

1) Avoid any stinging animals with powerful nematocysts. This means fire corals (Millepora spp.) and anemones should be excluded from the seahorse reef, and any corals with polyps that feel sticky to the touch should be used with discretion and only after careful planning. When a seahorse brushes up against them or attempts to perch on them, the nematocysts or stinging cells of these animals can penetrate the seahorse’s skin and damage its integument. Needless to say, this causes pain and discomfort and can leave the seahorse vulnerable to secondary bacterial and fungal infections, which may take hold at the site of injury. Short polyped stony (SPS) corals are generally fine, but large polyped stony (LPS) corals should be regarded with caution, as discussed in more detail below.

2) Water movement and circulation must be managed as previously described. Corals that require powerful surge or overly strong water currents could overtax the limited swimming ability of Hippocampus unless slack water areas the seahorses can retreat to when needed are also provided.

3) The corals must be able to withstand being used as hitching posts by the seahorses from time to time; that is, they cannot be so delicate that having a seahorse’s grasping tail anchored around them could cause them any harm. For instance, soft corals may retract their polyps when a seahorse perches on them. This can be harmful to their health if it becomes a chronic problem, because many corals rely on their polyps to absorb light and convert it to energy via photosynthesis. Be sure to watch any soft corals and hermatypic corals to make sure they are not closed up for extended periods. Normally, they adjust to the seahorses’ presence and unwelcome attention after a while, and remain contracted only briefly after each contact. After repeated exposures to grasping tails, each such incident elicits a weaker response, so they tend to extend their polyps sooner and sooner after being disturbed (Delbeek, Oct. 2001).

4) Avoid Tridacna clams and similar bivalve mollusks. Sooner or later a seahorse will perch on them with its tail between the valves and the clam’s powerful adductor muscle will clamp down on it like a vise. At best this will be a very stressful experience for the unfortunate seahorse, since it can be the devil’s own business trying to persuade the stubborn mollusk to release its struggling victim! At worst, it can result in serious injury or permanent damage to the seahorses tail (Giwojna, unpublished text).

5) Beware of unwanted hitchhikers that may have come in on your live rock unbeknownst to you and which can harm seahorses, such as fireworms, mantis shrimp, or Aptasia rock anemones. When setting up a reef system for seahorses, it’s a wise precaution to pre-treat your live rock with a hypersaline bath to drive out such pests beforehand because they can be very difficult to remove or eradicate once they make themselves at home in your aquarium (Giwojna, unpublished text).

As long as the specimens you are considering for your seahorse reef satisfy these requirements, anything goes! Some of the good and bad candidates for such a reef system are discussed below:

Seahorse-Safe Corals

Soft corals have very little stinging ability and generally make good choices for a modified mini reef that will include seahorses (Delbeek, Oct. 2001). This includes most mushroom anemones (corallimorpharians). However, as Charles Delbeek cautions, “One notable exception is the elephant ear mushroom anemone (Amplexidiscus fenestrafer). This animal is an active feeder on small fish and will envelope them whole with its mantle then slowly digest them by extruding its digestive filaments into the space created. No small fish are safe with these animals in the tank (Delbeek, Oct. 2001).”.

Hippocampus also does very well with zooanthids and colonial polyps in general. But the hobbyist must be sure to observe a couple of precautions when handling the zoanthids and placing them in your aquarium.

First and foremost, many of the commonly available Zooanthus (button polyps) and Palythoa (sea mats) species contain a very toxic substance in their mucous coat known as palytoxin, which is one of the most poisonous marine toxins ever discovered (Fatherree, 2004). Palytoxin can affect the heart, muscles, and nerves, resulting in paralysis or possibly even death, and many hobbyists have reported numbness, nausea and/or hallucinations after merely touching these corals (Fatherree, 2004). When you handle zoanthids and palythoans, you cannot help picking up some of their protective slime on your fingers, and so much as rubbing your eye, picking your nose, or a small cut on your finger can be enough to land you in the hospital. When handling Zooanthus are Palythoa species, it’s very important to wear disposable latex gloves, avoid touching your mouth or eyes, and carefully dispose of the gloves immediately afterwards (Fatherree, 2004).

Secondly, zoanthids and other soft corals such as mushrooms may wage border battles if you place them in close proximity to each other (and the zoanthids almost always lose out to the mushrooms in these skirmishes). So be sure to allow adequate space between the colonies. Some rapidly growing Zooanthus colonies can be aggressive to soft and stony corals alike as they rapidly spread over the rockwork, but in general they are quite peaceful, and you can always slow down their rate of growth by reducing the nutrient loading in the aquarium.

Other low light corals that should be suitable for a seahorse reef include genera such as Cynarina, Scolymia, as well as non-photosynthetic gorgonians such as Subergorgia and Didogorgia, and perhaps wire corals such as Cirripathes spp. (Delbeek, Nov. 2001).. However, supplemental feedings of zooplankton may be required to maintain these corals in good health.

The hard or stony corals fall into two categories depending on the size of their polyps. The small polyped stony (SPS) corals have tiny polyps that extend out of minute openings in the stony skeleton, and generally have weak stings that should not pose a threat to seahorses. Depending on conditions in the tank, SPS corals such as Acropora, Montipora, Pocillipora, Porities, Seriatopora and Stylophora can be tried freely at your discretion (Delbeek, Oct. 2001).

The large polyped stony (LPS) corals, however, are generally best avoided altogether. These include genera such as Catalaphyllia, Cynarina, Euphyllia and Trachyphyllia that have large fleshy polyps which often have tentacles equipped with powerful stinging cells. The Euphyllia and Catalaphyllia have the most powerful nematocysts among the LPS corals, and can deliver stings that are stronger than most anemones (Delbeek, Oct. 2001).

Some of the soft corals and stony corals that generally do well with seahorses in a modified reef tank are listed below. (By no means is this intended to be a comprehensive list, but rather just a few examples of suitable corals to serve as general guidelines when stocking a reef tank that will house seahorses):

Finger Leather Coral (Lobophyton sp.)
Flower Tree Coral – Red / Orange, (Scleronephthya spp.)
aka: Scleronephthya Strawberry Coral, or Pink or Orange Cauliflower Coral
Christmas Tree Coral (Sphaerella spp.)
aka: the Medusa Coral, Snake Locks Coral, or French Tickler
Cauliflower Colt Coral (Cladiella sp.)
aka: Colt Coral, Soft Finger Leather Coral, Seaman’s Hands or Blushing Coral.
Toadstool Mushroom Leather Coral (Sarcophyton sp.)
aka: Sarcophyton Coral, Mushroom, Leather, or Trough Corals.
Bullseye Mushroom Coral (Rhodactis inchoata)
aka: Tonga Blue Mushroom, Small Elephant Ear Mushroom (rarely)
Clove Polyps (Clavularia sp.)
Stick Polyp (Parazoanthus swiftii)
Green Daisy Polyps (Clavularia sp.), Indonesia
Orange & Green Colony Button Polyps (Zooanthus sp.), Fiji
Pulsing Corals (Xenia spp.)
Red Ricordea (Ricordea sp.), Indonesia, occasionally Solomon Islands
Lavender Hairy Mushroom (Actinodiscus sp.), Tonga
Pimpled Mushroom (Discosoma sp.), Indonesia
Purple Gorgonians

Lighting for a Seahorse Reef

If at all possible, metal halides should be avoided for a reef tank that will include seahorses. In addition to providing high-intensity lighting, the metal halides also tend to generate a lot of heat, and as you know, heat stress can be very detrimental to seahorses. Most of the subtropical/tropical seahorses do best at temperatures of around 73°F-75°F (23°C-24°C); so avoiding temperature spikes above 80°F (27°C) is very important. This can be very difficult to manage with metal halide lighting. In addition, seahorses don’t like excessively bright light and they may go into hiding, seeking shaded areas amidst the rockwork, if the lighting is too intense for their comfort level. And the seahorses won’t look their best and brightest under metal halides because they will produce excess melanin (black pigment) in order to protect themselves against the harmful ultraviolet radiation they associate with intense light, and darken as a result. For instance, Jorge Gomezjurado reports “…I have exposed yellow seahorses to strong metal halide and they have turned black in few hours.” So it would be a shame to display brightly colored seahorses under metal halide lighting in a small, close system aquarium.

All things considered, power compact lighting or LEDs with medium intensity are a better alternative for a seahorse reef. I prefer the power compacts because they allow me to provide my seahorses with a natural day/night period that includes twilight periods at “sunrise” and “sunset.” To accomplish this, I like the power compact (PC) light fixtures that include two tubes — one actinic and one daylight fluorescent — with dual ballasts so that each ballast can be placed on a separate automatic timer. I like to have the bluish actinic come on before the daylight tubes and stay on after the daylights go off, thereby providing a simulated dusk and dawn (Giwojna, unpublished text). This is important for seahorses since they conduct most of their courting and breeding in the early morning hours under twilight conditions. It’s a neat effect and fish and invertebrates can then anticipate “lights out” rather than being plunged into total darkness at night or suddenly thrust into bright light in the morning. I also adjust the timers to lengthen or shorten the daylight periods in accordance with the changing seasons. I find that maintaining a natural cycle this way aids reproduction (Giwojna, unpublished text).

Basically, I find PC lighting to be a good compromise for a seahorse system. Power compacts provide plenty of light for macroalgae or the seahorse-safe soft corals in a modified reef system without being too bright or generating too much heat, and the dual ballast system allows for a natural day/night rhythm that changes with the seasons. The resulting dusk and dawn facilitate courtship and help the seahorses maintain a natural reproductive cycle (Giwojna, unpublished text).

Although they are very costly, system such as the Solaris LED Illumination Systems are another good option for a seahorse reef. The Solaris LEDs can provide the spectrum of light and intensity needed by light-loving corals without the same concerns regarding overheating that make metal halides undesirable, and that’s a huge plus for the seahorse keeper. Aside from generating less heat, they also provide very considerable energy savings and the longevity of the LED is also superior to metal halide lamps. Best of all, the flexibility and adjustability of the Solaris LED Illumination System allows you to independently set the lights to duplicate sunrise, daylight, cloud cover, sunset, and even the lunar cycle. They certainly are very expensive, but they have some wonderful advantages over the conventional metal halide lighting, particularly for seahorses. However, because of the cost factor, I prefer PC lighting for a seahorse tank with live corals myself.

Of course, for seahorse keepers who do not have live corals in their corrals, standard fluorescent bulbs or tubes are more than adequate. For all intents and purposes, you really can’t go wrong no matter what lighting system you chose as long as you avoid overheating and provide both shaded areas where your seahorses can escape from light altogether and well-lit areas where they can bathe in the light as they please.

One good way to accomplish that is to keep the coral and inverts that require stronger lighting at one end of the tank, which is brightly illuminated, and keep the other end of the tank shaded to accommodate the seahorses, reserved for corals that don’t need high-intensity lamps. If need be, you can also provide shaded areas by positioning sections of aluminum foil atop your aquarium that are the right size and shape to cast shadows where you want them below. You will find your seahorses will move into and out of the light often, seeking the comfort level that suits them at the moment.
<Close quote>

And this is what Charles Delbeek has to say about keeping seahorses in reef systems:

<Open quote>
There has been a lot of interest lately in keeping sea horses in reef aquaria. Although it is possible to do so, there are some things that need to be taken into consideration. Most reef tanks that house corals also have a great deal of water movement. When combined with overflows, it is not uncommon for sea horses to be trapped against or even go over, overflows. Powerheads are also often used and can be death traps for sea horses if the intakes are not properly screened off. To keep sea horses in reef tanks one really must foresee all the possible ways that they could be injured and to take precautions against this happening.

Many corals are powerful stingers, but these belong mainly to the stony coral families. Most soft corals have very little stinging ability and will not harm sea horses. However, since sea horses can grasp onto soft corals with their tails they can cause the coral to retract its polyps. This can be a problem if the coral relies on its polyps to capture light to provide the energy it requires to survive. Fortunately in most cases, the coral will habituate to the constant irritation caused by the sea horse and will not retract its polyps as frequently as in the beginning. The observant aquarist should keep an eye on their soft corals to insure that they are not remaining closed for long periods of time.

In the case of stony corals there are two main groupings to be considered. The small polyped stony (SPS) corals consist of genera that have small polyps that extend out of very small openings in the skeleton. These would include genera such as Acropora, Montipora, Pocillipora, Porities, Seriatopora and Stylophora. These SPS corals are generally considered to be weak stingers and should not irritate sea horses very much. However, the same precaution I mentioned for soft corals also applies to SPS corals. The second major grouping are the large polyped stony (LPS) corals. These include genera such as Catalaphyllia, Cynarina, Euphyllia and Trachyphyllia that have large fleshy polyps often with tentacles that can have powerful stinging cells. Of these the Euphyllia and Catalaphyllia are the strongest stingers, and any sea horses placed into tanks with these corals should be carefully observed.

Despite what many people think, sea horses are quite effective swimmers and can hold their own in strong currents. However, in the confines of an aquarium, it is not impossible for them to come into contact with stinging corals if suddenly caught in a very strong current. The aquarist needs to take this into consideration when placing water returns and corals in the aquarium. People have been keeping fish with corals for several years now and the instances where fish have been taken by corals are few and far between, but it does happen occasionally. Sea Horses, like any other fish, have a natural ability to avoid most powerful stinging corals, and the slightest touch is enough to reinforce this natural avoidance behaviour.

Other invertebrates that sea horses should do well with include zoanthids, corallimorpharians (mushroom anemones), sponges, sea cucumbers, shrimp and the smaller detritus or algae feeding snails, worms and crabs. One notable exception is the elephant ear mushroom anemone (Amplexidiscus fenestrafer). This animal is an active feeder on small fish and will envelope them whole with its mantle then slowly digest them by extruding its digestive filaments into the space created. No small fish are safe with these animals in the tank.

Charles Delbeek
<close quote>

Okay, that’s the quick rundown on keeping seahorses in a modified reef tank that will include live corals, Kayle. Having explained all of the above, I should also point out that Mustangs or the Sunbursts (Hippocampus erectus) often thrive in suitable reef tanks, where they benefit from the optimum water quality, natural surroundings, and abundant copepods and amphipods in typical well-established reef systems.

3. I’m pretty sure that you guys breed at 75 degrees. Yet on your care sheets there is a range given 68F – 82F (Optimum temperature 75 – 78F) for the H. Erectus as an example. So I would assume I could safley keep my water at 76 – 77 safely or would that increase the risk of disease?

Yes, that’s correct – tropical Ocean Rider seahorses are maintained at a stable water temperature of 75°F.

The seahorses at the Ocean Rider aquaculture facility in Hawaii do just fine at a temperature of 76°F-78°F, but in the home aquarium, they will be experiencing much different conditions in a small, close system tank that is subject to considerable temperature variations. The average aquarist’s seahorse tank is relatively small and uses artificial saltwater and artificial lighting, and the lighting is a heat source that can raise the temperature of the small aquaria significantly over the course of the day. More importantly, the smaller aquariums can experience harmful temperature spikes during summertime heat waves. In my experience, the home hobbyist should strive to maintain stable water temperatures in the 72°F-75°F range in order to compensate for these other factors. In general, as a rule, all seahorses do better at the lower end of their acceptable temperature range then at the upper end of their comfort zone, particularly in the small, closed system aquariums of the home hobbyist.

As you know, Kayle, heat stress is extremely debilitating for seahorses and, in my experience, it is associated with more disease problems and mortalities in the home aquarium than any other factor. There are number of reasons for this. For one thing, elevated temperatures can have a very detrimental effect on the immune system of fishes. This is because many of the enzymes and proteins involved in their immune response are extremely temperature sensitive (Olin Feuerbacher, pers. com.). Some of these protective enzymes can be denatured and inactivated by an increase of just a few degrees in water temperature (Olin Feuerbacher, pers. com.). So when seahorses are kept at temperatures above their comfort zone, their immune system is compromised and they are unable to fend off diseases they would normally shrug off.

At the same time heat stress is weakening the seahorse’s immune response, the elevated temperatures are increasing the growth rate of microbes and making disease organisms all the more deadly. Research indicates that temperature plays a major role in the regulation of virulence genes (Olin Feuerbacher, pers. com.). As the temperature increases, virulence genes are switched on, so microorganisms that are completely harmless at cooler temperatures suddenly become pathogenic once the water warms up past a certain point. Thus both the population and virulence of the pathogens are dramatically increased at higher temperatures (Olin Feuerbacher, pers. com.).

This is true of Columnaris and certain types of Vibrio. At cool temperatures these bacteria are relatively harmless, but at elevated temperatures they become highly contagious, virulent pathogens that kill quickly. Neil Garrick-Maidment, director of the Seahorse Trust in the UK, reports that he stopped a deadly outbreak of Vibrio among his Hippocampus capensis dead in its tracks and cured the seahorses simply by cooling their aquarium down to 18°C (64.4°F) for a period of weeks. The bacteria simply no longer presented a problem at that temperature.

Here’s what Olin Feuerbacher reports regarding the effect of temperature on bacterial infections. Olin is a marine biologist who is now a Molecular Biologist and a member of the research staff at the Arizona Genomics Institute, and who runs a small aquaculture business raising clownfish, gobies, a bit of coral, and all sorts of odd food items including a lots of pods, microalgae, etc. He is also a seahorse keeper and has done a lot of research in tropical diseases. He is a grad student working on marine microbiology, mainly ocean borne human pathogens, and his specialty has been the Vibrio bacteria!

In short, Olin really knows his stuff when it comes to this sort of thing. Here are his thoughts on bacterial infections in seahorses:

They typically start as a secondary infection after either mechanical damage or parasites or cnidarian stings. Once established, they are difficult to control. This is due in part to the fact that they are typically normal flora in all tanks. They are generally benign until they get an opportunity to invade. As for the importance of avoiding heat stress when it comes to bacterial infections (or the value of maintaining reduced temperatures when fighting a bacterial infection), this is what he has to say:

It is interesting that you mentioned the elevated
temperatures. I think this is a critical factor in a
number of ways. First, elevated temperatures can have
many adverse effects on the immune status of many
organisms. Many of the enzymes and proteins involved
in an immune response are very temperature sensitive.
When studying an outbreak of vibriosis in echinoderms
during an El Nino event in the Sea of Cortez, I found
that several defensive enzymes in the echinoderms were
inactivated by a rise of only a few degrees in water

In addition to the effects on the hosts, water
temperature may have very significant effects on the
pathogens as well. First, elevated temperature will
obviously increase the rate of microbial growth.
Perhaps more importantly, recent research has
implicated temperature as a major factor in the
regulation of virulence genes. When in the cooler
pelagic environment, a bacteria wants to conserve
energy, so virulence genes will not be expressed since
there is probably no host. However, in warmer temps,
these genes can be turned on resulting in pathogenesis.

This is especially true for bacteria such as the
Vibrios which exist both as normal aquatic flora and as
pathogens in many mammalian species with our nice warm
digestive tracts etc. One particularly interesting
study showed that the coral pathogen Vibrio strain AK1
was completely benign, despite heavy colonization, in
corals at one temp (I forget exactly what, I think it
was about 25C), but when temperature was raised by 3
degrees, all of the virulence genes in the Vibrio’s
pathogenicity island were turned on. This resulted in
severe infection and rapid death of the corals. Bad
news for aquarists, but I still think this kind of gene
regulation is really cool!

So raising or dropping the water temperature just a few degrees can make a huge difference. Likewise, here are Neil Garrick-Maidment’s observations on the importance of water temperature when treating a Vibrio infection:

I am not sure if it is of any help but I recently had a problem with vibriosis
in Hippocampus capensis coupled with a couple of gas bubbles in the end of the
tail. Having tried a number of treatments in the past that havn’t worked I took
a slightly more drastic approach this time and dropped the temperature from 23°C (73.4°F) down to 18°C (64.4°F) having first isolated the infected animals into a separate tank. I then left them like this for 4 weeks after which I increased the
temperature slowly up to 21°C (70°F), which it still is. After the second week
the vibriosis had gone completely (and has not returned) and the gas bubbles
were gone after the third week. In all the time the temperature was low the
animals reduced their feeding and it has now increased with the raising of the
temperature and they since gone on to have two broods of fry.

Best wishes,

Neil Garrick-Maidment
Seahorse Project Co-ordinator

Aside from the detrimental effects heat stress has on the immune system of seahorses and the virulence of pathogens, it also has an adverse affect on the breathing of seahorses and is responsible for many deaths by asphyxiation. Elevated water temperatures increase the metabolism of seahorses, and therefore their consumption of oxygen, at the same time that the rise in temperature is reducing the amount of dissolved oxygen the water can hold. That creates a dangerous situation for seahorses and may well result in respiratory distress and rapid, labored breathing.

Seahorses are more vulnerable to the low O2/high CO2 levels associated with heat stress 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, seahorses are thus especially vulnerable to low oxygen levels and asphyxia.

In short, Kayle, if you can maintain a stable water temperature of 76°F-77°F, the seahorses will be well within their comfort zone, but it’s very important to prevent the water temperature from approaching 80°F or above for any length of time for the reasons discussed above.

Best of luck with your new seahorse setup, Kayle.

Pete Giwojna, Ocean Rider Tech Support

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