Dear WW:

Pete Giwojna

Dear WW:

The short answer to your question is, “Yes.” Providing the seahorses have the same temperature requirements and aquarium requirements, were born and raised at the same aquaculture facility, and the aquarium is large enough to safely support both types of seahorses, keeping more than one species of seahorse together in the same aquarium can certainly be done.

As for whether the different species of seahorses will interbreed when maintained together in the same aquarium, that is relatively uncommon and unlikely to occur, but it does sometimes happen.

Interspecific hybridization has been known to occur between a number of species in the aquarium, on rare occasions, WW. For example, Hippocampus erectus and Hippocampus reidi seahorses will occasionally interbreed in the wild, and I know of one or two instances in which Hippocampus barbouri and Hippocampus comes seahorses have crossbred in the aquarium.

So it’s most definitely not unheard of for certain species to crossbreed and produce viable offspring in captivity, and that’s not necessarily a bad thing on the hobbyist level, since the hybrids that result can sometimes be very attractive seahorses and may even benefit from the phenomenon of hybrid vigor. However, that doesn’t apply to a commercial aquaculture facility, WW.

Crossbreeding is generally frowned upon and considered undesirable in aquaculture for a number of reasons, which are outlined in the following position statement from Project seahorse:

Interspecific hybridization of seahorses and pipefishes

A position statement from Project Seahorse

Project Seahorse cautions against mating across different species (hybridization) of seahorses and
pipefishes (syngnathids). Trade in hybrid offspring of such matings may compromise captive
breeding programs and release of hybrids poses high risks to wild populations. In order to reduce
the potential for hybridization we recommend that anyone currently holding or intending to hold
• maintains single-species tanks wherever possible;
• considers giving the name of any doubtful syngnathids to the genus level only, e.g., naming
seahorses simply as Hippocampus spp;
• avoids distributing any syngnathids that remain unidentified at the species level without full
disclosure of their status;
• refrains from acquiring syngnathids for any collective breeding program without reliable
information on their origins and taxonomy (this may require genetic or morphological
• uses syngnathids with questionable origins or taxonomy only for display or educational work
and control their populations carefully.

Aquarists will need to be careful about avoiding hybrids, especially as such general confusion about
sources and identities (taxonomy) of syngnathids still prevails. As with all other species, syngnathid
species are generally reproductively isolated from each other in the wild. Biological or physical
barriers usually preclude hybridization in the wild, even where species’ ranges overlap. The
aquarium environment can actually promote hybridization by removing these barriers, and by
holding geographically separate species together at high densities.

Aquarists should also note that hybrids – which may appear desirable because of their unusual
features – might display reduced survivability and reproductive potential when compared with the
parent species.

Project Seahorse is concerned that syngnathid hybridization in the aquarium community will hamperthe development of collective programs of captive breeding (see Project Seahorse Aquarium position statement). A key goal of such work is to ensure that the most genetically diverse and healthy populations of syngnathids, of known origin and founder number are retained. Achieving this goal means that all information about the animals involved must be very accurate, and fully shared.

It is important to realize that release of hybrids, accidentally or by intention, may severely damage
wild syngnathid populations (see Project Seahorse Releases position statement). Public zoos and
aquaria have guidelines on disposal of animals but these do not control the fate of animals in the
private domain. Hybrids that survive release may successfully mate with wild syngnathids and
potentially introduce new and harmful genetic material to the native population, thereby reducing
survival, growth and reproductive output. Different populations and species of syngnathids that
have evolved in different geographic regions and under different conditions display local
adaptations, regulated in part by their genetic material.

Successive breeding with released hybrid syngnathids could gradually destroy local population
adaptations that have taken millions of years to evolve, reducing the population’s chances of

For those reasons, WW, as a High-Health aquaculture facility, I can assure you that there is NO unauthorized breeding at Ocean Rider. Each strain of seahorses is necessarily kept in a biosecure area that strictly segregate it from all of the other types of seahorses. In short, the many different species of seahorses raised at Ocean Rider are never mixed together; each line has its own biosecure area, its own rearing tanks, and its own grow out tanks.. Needless to say, this effectively presents crossbreeding and interspecific hybridization.

In home hobby tanks, however, where different species of seahorses are often mixed freely, crossbreeding or interspecific hybridization does occasionally occur, but it is quite uncommon, especially when seahorses have potential partners of their own species available to them. The prolonged, elaborate courtship ritual that seahorses go through before mating occurs generally prevents seahorses from different species from breeding successfully. Suffice it to say that seahorses are much, much better at species recognition than we are, and that given a choice, they almost always prefer to mate with their own kind. Almost always.

But there are also other considerations besides water temperature that you must keep in mind before you attempt to keep different seahorse species together in the same tank, WW, and we need to discuss those factors as well.

As an experienced seahorse keeper, WW, you may have heard about the concerns many hobbyists have expressed in the past about mixing various seahorses from different breeders or different parts of the world. There is a school of thought that maintains that mixing different species of captive-bred seahorses raised by breeders in different parts of the world can be a recipe for disaster. In theory, to do so could risk introducing pathogens from one part of the world to seahorses from another region which have little or no resistance to them (Leslie Leddo, et al., pers. com.). I like to call this theory the “smallpox syndrome,” and the rationale behind it goes as follows:

The “Smallpox Syndrome”

When it comes to colorful, captive-bred seahorses, hobbyists in the USA are blessed with an abundance of riches. There are now 21 distinct varieties of cultured seahorses available in the US, with different color morphs and new farm-raised species hitting the market all the time. We are fortunate indeed to be living in a time when mariculture is undergoing a renaissance and seahorse keeping is emerging from the Dark Ages of the hobby when wild-caught seahorses were the only option and entering into a more enlightened era where conservation and preservation are the watchwords of the day. This is truly the dawn of a Golden Age for seahorse keepers when fabulous farm-raised specimens abound and we no longer need to exploit wild populations for aquarium specimens.

Most of these domesticated seahorses are raised in Hawaii and Australia, with more and more captive breds beginning to trickle in from Florida and the United Kingdom, Sri Lanka, Asia and Indonesia, with one species (H. ingens) being raised in Mazatlan, Mexico. In looking over this list, it immediately becomes apparent that our captive-bred jewels are raised in vastly different parts in the world. The big seahorse farms, aquaculture operations, and major breeders are all separated by thousands of miles, literally oceans apart from each other.

As wonderful as it is to be able to enjoy cultured seahorses from all around the world, this also presents a potential problem. When we keep seahorses from different parts of the world together in the same aquarium, in theory we may risk exposing our prized pets to exotic pathogens and parasites to which they may have little or no resistance.

I should hasten to add that the reason this may present a potential danger is not because domesticated seahorses have naïve, undeveloped immune systems. On the contrary, captive-bred seahorses have been rigorously selected for disease resistance for many generations and have emerged from this relentless weeding out process as remarkably hardy specimens with an aggressive immune response. It has been demonstrated time and time again that captive-bred seahorses have superior immune systems and greater disease resistance than wild-caught seahorses.

Rather, the potential concern is that captive-bred seahorses reared in Hawaii, for example, may have developed their resistance to somewhat different strains of disease organisms than the ones seahorses raised in Florida or Australia or the UK have built up an immunity to, and vice versa. Different strains of Pseudomonas and Vibrio bacteria, as well as different species of parasites such as Glugea and Uronema, are prevalent in different parts of the world. When we bring seahorses from different breeders in different parts of the world together, or bring different species together, there is a possibility they could be exposed to strains of such pathogens they have never encountered before and are thus ill-equipped to deal with.

The potential danger is akin to the situation when the early explorers from the Old World first encountered American Indians in the New World. These initial encounters were generally peaceful and friendly, but they proved utterly disastrous for the Indians who died in droves from diseases such as smallpox they had never been exposed to before. Even relatively harmless afflictions such as measles decimated the tribes. Many times the Europeans explorers fared little better, as exotic New World diseases such as yellow fever and malaria cut a swathe through their ranks. I like to refer to that scenario as the smallpox syndrome.

The problem was not that the Indians or the explorers had inferior immune systems. On the contrary, the tribes were tough as nails, supremely well adapted to their natural environment, just as the Europeans were perfectly adapted for the climate and conditions in the Old World. The problem was that when the two groups were suddenly thrown together, they were introduced to new afflictions for the first time with which they were unable to cope. They had not gradually built up resistance to these new diseases over many generations as susceptible individuals were weeded out of the population and the hardier individuals developed immunity.

We see the same thing on a lesser scale today every year as influenza pandemics sweep around the world during the flu season. Typically an Asian strain of influenza arises in the East and spreads to Europe and North America via international travelers, where it proceeds to wreak havoc because Westerners have no resistance to the new strain. Hence the annual ritual of flu vaccinations in an attempt to curtail such outbreaks.

This has led to concerns among seahorse keepers that we risk the same sort of problems when we keep compatible seahorses raised in different parts of the world together in the same aquarium. It’s an interesting theory that has some merit and it is certainly based on a plausible scenario. At present, however, there is no data to support the notion that maintaining a mixed community of seahorses from different breeders around the world results in more disease problems than species-only tanks or systems holding only seahorses from the same breeder (hence the same part of the world). All we have to go on at this point are anecdotal reports from hobbyists, which can be notoriously unreliable.

That’s the rundown on the “smallpox syndrome,” WW. In all honesty, I have no idea if such concerns are valid and justified or not. I can tell you that I know many hobbyists who keep seahorses of different species from different sources and breeders together with no problems whatsoever. And I know many other hobbyists who have experienced various problems when they mixed seahorses of different species. Likewise, I know of many hobbyists who keep seahorses strictly from one breeder, yet still experience various health problems, up to and including tank wipeouts from infectious diseases. Thus far, I haven’t been able to detect a pattern to these reports and incidents, other than the obvious fact that many times seahorses (or compatible tankmates for seahorses) obtained from the LFS have proven to be disease vectors that introduced pathogens or parasites into the main aquarium and that, of course, wild-caught seahorses are much more disease prone than hardy captive-red-and-raised seahorses. The one other consistent report regarding seahorses that I hear over and over again, and that I know to be a fact, is that the new Hippocampus kelloggi seahorses that have been making their way to the US from Vietnam and Asia lately are very fragile and disease prone, and have been dying off in droves, particularly when they are kept under tropical conditions. But that is happening regardless of whether they are kept in species tanks by themselves or in community tanks or any other type of setup. The H. kelloggi just appear to be very delicate aquarium specimens at this stage in their development and you should avoid them at costs.

Personally, I have not put much stock in the Smallpox Syndrome with regard to seahorses in the past. Up to now, I have tended to discount such reports largely because we aquarists do not have any such concerns when it comes to other marine fish and invertebrates. Most marine aquarists maintain a community tank of colorful reef fish and freely mix fish and invertebrates from the Philippines and Indonesia with other marine fish and inverts from the Atlantic and Australia or the Red Sea without any worries whatsoever regarding a “smallpox syndrome” effect decimating their aquariums. Likewise, reef keepers freely mix various corals and frags from different aquaculture facilities that originated in different oceans around the world without any such fears. Providing they quarantine the new arrivals to make sure they are healthy before they introduce them to the main tank, most such community tanks and reef systems do just fine, so it isn’t really clear to me why seahorses should be considered an altogether different case that must be strictly segregated by species or by breeder.

As for myself, I have never hesitated to mix different species together in the same aquarium providing they have compatible aquarium requirements in terms of their preferred aquarium parameters and feeding habits, but then again, I get all of my ponies from Ocean Rider, which is the world’s only High-Health seahorse farm, so perhaps I have been lulled into a false sense of security due to the fact that I have never experienced any difficult these mixing different Ocean Rider species together. Over the years, this includes keeping the Brazileros (Hippocampus reidi), Spikeys (Hippocampus barbouri), and Gigantes (Hippocampus ingens) together with Mustangs and Sunbursts, as well as exotic strains such as Pintos and Fire Reds.

That’s my thinking on the matter, WW. However, I should add that I think it is best for new seahorse keepers to stick to a single species of seahorse in order to simplify things while they are learning the ropes and becoming accustomed to providing ideal conditions in the best possible care for the particular ponies of their choice.

And, to be on the safe side, I always advise experienced seahorse keepers who are considering keeping different species together to stick with different strains of High-Health Ocean Rider seahorses, which I know from my own personal experience can be kept together quite successfully.

Aside from temperature considerations and any concerns about the smallpox syndrome, in many cases it’s best to set up a new tank anyway when you want to add more seahorses to your collection simply to avoid overcrowding. When your existing tanks are running along smoothly and trouble free, why risk upsetting the balance by adding new specimens to the established aquaria? In such a situation, it’s generally a much better idea to put up a separate aquarium tailor-made for the new acquisitions that have caught your fancy. In short, it makes good horse sense to segregate seahorses obtained from different breeders for a number of reasons.

In your case, WW, if you would like to combine different types of seahorses and have them breed together readily, then I would suggest that you stick with Ocean Rider Mustangs and Sunbursts, which are different color morphs of the same species (Hippocampus erectus). As such, they have identical aquarium requirements, are equally hardy, and, of course, will interbreed freely. They make ideal tankmates for one another.

Ocean Rider offers many special offers and package deals at bargain prices, and you may well be interested in one or more of these special packages, WW.

If you copy the following URL, paste it in your web browser, and press the “Enter” key, it will take you directly to the proper area of the Ocean Rider website ( for all of the Special Packages:

Best wishes with all your fishes, WW!

Pete Giwojna, Ocean Rider Tech Support

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