Keeping seahorses in the aquarium


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Nathan Hill freely admits to being captivated by the charm of the seahorse. Here he explains why he never tires of this unique creature.

Love for the seahorse seems to depend on where you are. In the UK you can visit any public aquarium and be entranced by their delicate movements; the way they seem to drift effortlessly from one anchor point to another.

However in the Far East you’d be more likely to see one dried and powdered, ready to become a bitter-strong tea in attempts to cure ailments from asthma to impotence — and pretty much everything in between.

There’s little credible evidence to suggest that seahorse flesh has any medicinal properties at all, but old habits die hard and seahorse medicine goes back a long way. These creatures apparently make for good eating too.

Many market stalls in the Eastern world will happily sell you deep-fried seahorse, often dipped into boiling fat while fresh and wriggling. Mix and match and you could have a scorpion on the

same skewer.

The seahorse itself seems a crazed scientist’s mix of spare parts. There’s the equine-looking head, from which the fish derives its name. There are independent eyes, Chameleonic in their attentiveness. The scaled exoskeleton is unlike most found in the fishy world, more insect than ichthys.

A dorsal fin at the back flutters like a flag in high wind and males carry bum-bags full of babies. To polish it all off, a moment of evolutionary craziness decided to put all of this atop the grasping tail of a marmoset.

The whole fish seems out of sorts with the rest of nature. Quite becoming then, that the scientific name for the genus Hippocampus is a Latin word for horse monster.

Seahorses take their taxonomic place among the pipefish, or Syngnathidae in the hobby.

Aside the obvious difference in shape an area that marks the two apart is the presence of a tail fin, or caudal fin in the pipefish, but this is never found in the seahorse. Then there’s the way the seahorse swims upright in a way almost every other fish doesn’t.

More species

Depending on your source, you’ll find a figure somewhere around the high thirties or low forties to account for the number of known species, but there are many more than this as I reason that we have not long been aware of the many pygmy seahorses that inhabit specific corals.

Pictures of these are becoming more abundant, with varieties that boast lavish and intense colours living among the branched arms of Gorgonia and other sessile invertebrates, supposedly making their homes for life.

Keeping seahorse in aquaria has never been easier, with an ever-growing fan base of aquarists taking the plunge. Some years back, keeping seahorses was frowned upon, citing difficulty in feeding the primary reason for general concern.

These fish are very stubborn when selecting food and only the freshest, wriggliest morsels will often do. In times when live foods were inconsistent and of questionable quality, keeping seahorses could be a struggle.

Captive breeding has played a huge role in this new-found ease of home keeping. A wild-caught specimen, used to specific food honed after a life of active hunting, knows little of the palatability of dead, frozen foods. As they are more frequently raised from fry in aquaria, they are being increasingly weaned on to and reared on frozen alternatives. It never hurts to ask your retailer if you can see the fish taking frozen foods before you’re inclined to purchase them.

There are issues too with frequency of feeding any variety. These are planktonic grazers in both the wild and aquaria, tethering themselves to something sturdy and seeing what treats the currents waft their way. One or two feeds a day won’t usually suffice and you should try lots of smaller feeds daily.

Depending on species, and specifically the size of fish, a wide range of foods will often be taken, as long as they are small and shrimp-like. Artemia is often used, but frozen varieties tend to be nutrient deficient; more shell than meat. Larger species tend to prefer the spindly, lobster-like Mysid shrimps and krill, smaller ones liking Calanus.

Forget flake food. I’ve yet to see a seahorse give it even a glance. Don’t offer too large a food either, as seahorses have a rigid, fused mouth with little flexibility.

In aquaria, they like things quiet and tank mates — if any — should be shy and retiring. Mandarins tend to blend quite well, as do some smaller gobies. Active fish are out, so forget angels or damsels.

Many inverts can be a no-go too. There’s a contradiction between inverts liking strong currents that bash them in every direction and the weak swimmers that get picked up by the lightest of flows and thrown into the tentacles of predatory anemones.

Marine plants are a big yes. Underwater flora provides the cover and security that many seahorses relish. I’ve found that the grassy, kelpy Caulerpa prolifera makes a superb home for many species which will roam endlessly searching for anything that moves.

Seahorse reproduction is a turning point of traditional sexual roles within animals. They are famed for the male ‘birthing’ the young from a pouch not unlike a wallaby. The female still produces the eggs, but rather than lay these in the water for the male to fertilise she lays them directly into his pouch.

Traditionally, it was thought he would then fertilise them within the pouch, but there’s contention as some authors claim the eggs are fertilised in the water during the exchange. We do know for sure that once inside the male the eggs are subject to a rudimentary placenta, with father producing nutrients transported into the developing eggs.

The seahorse’s pouch has been the undoing of many a fish owned by inexperienced aquarists. We tend to think nothing of moving our fish from tank to tank, albeit carefully with nets. We probably rank among some of the world’s best anglers, but net use on seahorse is perilous…

The fish’s inflexible outer skeleton does not really support its body weight out of water and the brooding pouch can easily fill itself with atmospheric air, creating a second swimbladder and pinning it to the surface of the aquarium.

You can remove gases from pouches, using tiny plastic tubes or pipettes, but these should be the recourse of only the most experienced fishkeeper. Hobby professionals will invariably use a submersible method of catching their stock, often a beaker — or even bagging the fish underwater.

Bloat panic!

Larger fish will show a greater fertility or fry-producing potential than smaller ones, with research showing that fry from bigger seahorses suffer lower rates of infant mortality, as well as an increased growth rate.

Broods of up to 200 are not unknown, but only among the largest and strongest seahorses.

During ‘pregnancy’ the male can become grotesquely bloated and some aquarists panic if unfamiliar with the process.

These creatures are revered as bonding for life, forming a monogamous relationship broken only by death. There may be truth in this belief, but studies have shown that females will often play the field, periodically interacting with other males.

The bond is one of the legends behind the fish’s desirability within the Chinese Medicine (TCM) trade; making them the ideal aphrodisiac for couples seeking to add a little spice to their relationships.

Fry are challenging to raise. The parents are protective, with any infanticide seemingly accidental; offspring being taken when mistaken for shrimpy morsels.

Feeding fry is a full-time job, maybe comparable to a child but without the crying at night. Food offered must be tiny and constant source of rotifers a necessity.

Newly hatched artemia should be used sparingly and enriched for a good 48 hours prior to use. Colonies of copepods will be gobbled if offered and, although sometimes difficult to culture, make a brilliant starter diet.

Be cautious with the fry. Even weak filters can suck them up and aiptasia, given the opportunity, will ‘gorge’ on them. If serious about raising the young then a specific rearing tank with impeccable water quality will be required.

Seahorses are found across a wide region, including the Mediterranean where they are often caught, dried, adorned with comedy eyes and sold to unsuspecting tourists. Some species are even found in British waters and public aquaria undertake research and conservation projects.

Seahorses are normally found in tropical regions, with most imported for the trade from the Indo-Pacific as well as Caribbean, although I frown on wild-caught seahorses, with their notoriously high mortality rates, in capture and transit. We as fishkeepers can vote with our wallets, so if we don’t want to play any part in fish deaths through transportation we should use our money wisely.

Where do I stand on seahorses? Ten years ago I’d have been hostile, discouraging the idea at inception. Nowadays, I’m on the fence.

If you have the time for these fish, and trust your retailer to get you a farmed specimen along with bundles of appropriate food, you’re in with a good chance. It’s not aquatic snobbery to say this fish is more for the experienced aquarist; it’s common sense.

I’ll argue that a delicate, living organism should only be taken on by someone who has both confidence and experience to provide for it. If you’re new to the hobby, sizing up a 30 l/6.6 gal aquarium and thinking a tank of seahorses might be nice in the office, then I’m still hostile.

Which one is right for me?

The species I’d recommend for the budding aquarist would be Hippocampus kuda. I’ve kept and bred these several times and find they lend themselves to aquarium life very well — provided conditions are right

These are large seahorses and as such are able to take a wider range of foods than smaller counterparts. However, this fish is a master of camouflage, able to alter the shades of its body to blend in with its surroundings. Several times I’ve fretted and sweated over a ‘missing’ fish only to find it directly in front of me!

Premium needs

Seahorses are among the most demanding of marine fishes regarding water quality. A wide range of salinities seem to be tolerated well, with most happy between a specific gravity of 1.021 and 1.025 at 25°C/77°F. However, that’s where the leeway ends.

Ammonia and nitrite will not be accepted, even at low trace levels, and nitrate must be controlled — as it would be for sensitive invertebrates. That means you need a large aquarium for a very small fish.

Temperatures can vary slightly from species to species, so research thoroughly before committing. As always, stability is the key to success.

Suitable stabling? Consider a refugium...

Housing a seahorse can be as difficult or as easy as you make it. The dilemma we face is in providing a large enough body of water to attain stability. These creatures are not big but sensitive and require a large volume.

Many pioneer fishkeepers would have kept these fish in individual aquaria, usually around 92-120cm/3-4’ long, with undergravel filters that limit the dangers of trapping or sucking up the weak fish.

That was all well and good, and many did well on this method, but only at the expense of a great input of labour. Those tanks needed a lot of water changing and much maintenance.

Now we have newer technologies at reasonable prices – assuming we can’t make things ourselves. One frequently seen advance is the refugium — the tank lashed on to a tank and much smaller than the main one, and a thriving community of life. These are ideal homes.

Most keepers have refugiums to help remove undesirable wastes from their main aquarium through natural processes not usually viable within the body of the aquarium itself.

A refugium requires slow flows, deep media (or mud) and often heavy growths of marine algae.

They tend to harbour large colonies of copepods which will periodically find their way into the main tank and provide an edible treat for the inhabitants.

So we have a smaller aquarium joined to a larger body of water – providing stability. We have ample shelter in the form of caulerpa. We have no irritating or boisterous tank mates. We have an abundance of small, edible creatures — and we have an very slow flow of water with no fry-gobbling pumps.

Perfect for seahorses…

No den for any dragons

At no point have I addressed Leafy sea dragons, which may appear vaguely similar to seahorses. I won’t go near these with a barge pole and neither should you.

Aside from being a protected species, these striking fish are the ultimate feeding challenge, requiring the finest water quality — certainly beyond anything I could manage.

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