A seahorse diary

Captive Bred, Captive Raised -- See the "Tank Raised, Tank Bred" paragraph below.

Character -- The seahorse species that are kept as pets tend to be sedentary.  Most or all seahorses are peaceful, although rare "seahorse fights" have been documented by aquarists.  In the aquarium many species are monogamous, but a few are downright permiscuous .  It is said that their mating behavior probably varies in captive life from the behaviors displayed in the ocean.  Tank-bred seahorses can be trained to eat out of their owner's hand and may even wrap their tails around a person's fingers.  Most seahorses do not display much individual personality, but their beauty and grace more than make up for that.  Nothing is more enchanting than looking into an aquarium and seeing seahorses!

Food -- All seahorses are carnivores; most eat minute crustations and small fish.  Their hunting technique is highly specialized in that they do not chase their prey, but sit very quietly and wait for it to swim by them.  Once the prey is within range, a seahorse can display amazing acrobatics while trying to reach it.

Fossil Record -- Despite its odd appearance which would suggest dinosaur-era beginnings, the seahorse is apparently not a remarkably ancient fish. A really ancient fish would be the Coelacanth, a fish with a history stretching back hundreds of millions of years, which was once thought to have gone extinct with the dinosaurs 65 million years ago but is now known to be alive, if somewhat threatened, in the oceans around Africa and Indonesia.  The oldest known seahorse fossil is a comparatively recent 13 million years old (see this site for pictures); the fossils that closely resemble the seahorses we know today are a mere 3 million years old (see Wikipedia for details).  Seahorses are thought to have originated in the Atlantic Ocean, but the reason for their unique set of adaptations seems to be unknown.  All recent discoveries of new seahorse species have been made in the Pacific Ocean or other seas around Southeast Asia and Australia.  Atlantic seahorses are the ones with the oldest fossil records, and are also the ones that keep turning up in unexpected places, such as the River Thames!

Habitat -- All seahorses are primarily marine fish, although a few species have been found living in brackish rivers.  It is not recommended that you attempt to convert your seahorses to brackish water at home, as their trips into brackish water in the wild seem to be temporary in nature. The fish occasionally sold as "freshwater seahorses" are actually freshwater pipefish.  These are related to seahorses, but real seahorses cannot live in fresh water.

Most seahorse species live in seagrass beds; others live in coral reefs.  There are a few that drift with ocean currents. 

These are not always tropical fish.  Some seahorses reside in such cool waters that they require chillers in their aquariums (an example is the Zulu-Lulu® seahorse); h. zosterae (dwarf seahorse) and h. erectus (lined seahorse) can withstand a wide range of temperatures in the wild but are happy at a steady room temperature of about 72 degrees F in captivity.

Lifespan -- In a captive environment, 1-2 years (small seahorses) to about 5 years (larger seahorses).  The lifespans of most wild seahorses are unknown.

Physical Characteristics -- These are real fish, but are highly adapted.  All seahorses have prehensile tails (meaning they use their tails like hands).  They are missing many of the fins that most fish have, including the tailfin.

A seahorse has no tongue or teeth. 

All seahorses swim upright, and are graceful but weak (and usually reluctant) swimmers.  Most species require frequent rest on "hitching posts" such as plants, corals, and slender rocks, but some can drift with ocean currents.  The species that hitch are generally (not always) found in relatively shallow water; the ones that drift can be sometimes be found in the middle of the ocean.

Each of a seahorse's eyes moves independently of the other.

Seahorses are vertebrates, meaning they have backbones.  Often they look bony and spiny, and may feel that way, but there are also many that are amazingly soft to the touch.

They are scaleless fish. 

Their digestive systems are basically just tubes that food passes through; that is to say they are incredibly inefficient, meaning that seahorses have to eat a lot.

Most seahorses are masters of disguise.  Many can change colors at will.

Relatives -- Pipefish (freshwater, brackish and marine) and weedy/leafy sea dragons (marine only) are the seahorse's relatives.  Marine pipefish make good aquarium companions for larger seahorses.  Freshwater pipefish may make a good "introduction to seahorses" choice for aquarists who are uncertain about taking the leap from freshwater to marine aquarium keeping, although these creatures can be difficult to feed because they require live fish.  Keeping brackish pipefish, and all brackish fish, is a mysterious part of the aquarium hobby that requires special and hard-to-come-by knowledge because of the water-chemistry requirements.  Leafy sea dragons (and the less-flashy weedy sea dragons) are not available to hobbyists.  Although they have been kept in public aquariums since about 1987, they have only reproduced in captivity since around 2002.  They are too threatened in the wild to consider collecting, and have proven quite difficult to keep alive in captivity.  They're also much too large for most home aquarists to consider keeping.

Reproduction -- Seahorses are livebearers.  Of course you probably know that in the seahorse world, the male fish give birth.   The fry of many species tend to be miniatures of the adults with no notable "baby" features; however, this is not always true.  Depending on the species, some fry drift around in the current, and others hitch immediately.  The species with fry that hitch are much easier to breed in captivity; these fry are generally born more "mature" than those that drift.

Size -- Seahorses vary in size from barely 1/2" tall (h. severnsi, h. satomiae, h. pontohi, h. denise, h. walea and h. debelius, the smallest known pygmy seahorses) to a whopping 14" tall (h. ingens, the giant seahorse).  It's a fairly safe bet that the largest seahorse species are already well-known, although the ocean is always yielding surprises.  "New" seahorses have been discovered at an amazing rate in recent years, but so far they have all been pint-sized. 

Species -- There are about 32 to 35 known seahorse species, and perhaps many more that are unknown.  About 8 of these are routinely sold as pets.  Some of the rest are totally unsuitable for captive life.  Six species (h. severnsi, h. satomiae, h. pontohi, h. denise, h. walea and h. debelius) have been discovered recently; of course they had been there all the time, but had been missed because they are all extremely tiny and match their surroundings well. 

There have been reports of different seahorse species interbreeding in aquariums, but no fry have been born as a result.

Tank Raised, Tank Bred -- Also known as "captive raised" and "captive bred;" sometimes "aquarium" raised or bred.  "Tank Bred" means that the seahorse was born and reared in an aquarium.  These seahorses are hardier in an aquarium environment, and many are trained to eat frozen food, which makes them easier to care for than their wild-caught cousins.  Some display bright colors that are not found in the wild.  "Tank Raised" only means that the seahorse has been exposed to aquarium life, but likely was wild-caught.  Some vendors will even take the trouble to train wild seahorses to eat frozen food, but this training sometimes seems to disappear rather suddenly, and with disasterous results.

Threatened or Endangered Status -- Endangered status varies depending on the species of seahorse.  As previously mentioned, h. capensis, the South African seahorse, is gravely endangered in the wild.  Due to overfishing and other issues, most species that live in the oceans of Southeast Asia are also disappearing rapidly, but are not officially on the endangered list.  The seahorses of the Americas are in a somewhat better position, but they, too, are threatened by pollution and the resulting loss of habitat, as well as collection for the aquarium trade.  In fact, it's safe to say that all seahorses are threatened and many face extinction within our lifetime, even if only one species is currently listed as being endangered.

For greater detail on the points and issues listed here, please see the book Dwarf Seahorses in the Aquarium by Alisa Wagner Abbott.  It is available at Amazon.com and Barnes & Noble.  This book is absolute required reading for anyone considering keeping dwarf seahorses.

Housing -- Your corral can be any tank 10 gallons or smaller.  A larger tank will make it very, very difficult to be certain that all your ponies are being adequately fed (see "Feeding" paragraph above).  The nice thing is that you don't need a cover on the tank, because seahorses can't jump!

Five gallons is optimal for a herd of up to 10 ponies; actually, a tank this size can house up to 20 adults.  If you take good care of the tank, you will have lots of fry and in the end, more adults than you ever wanted -- and this can happen in no time at all.  So it's probably best to have somewhat fewer ponies to start with -- but not too few!

Bigger seahorses must be kept in larger tanks (bigger than 20 gallons for some, bigger than 40 gallons for others) that are around 3 times the height of the seahorse.  This is not a concern with dwarf seahorses, probably because there isn't a tank around that isn't 3 times their height. 

Sponge filters are best for these little guys.  Aeration must be provided 24 hours a day; make sure the airstone you use is safe for marine use.  Keep the water flow as low as possible without having the water go stagnant. 

I'll be experimenting with using an 8-gallon marine BiOrb with my new ponies.  I've observed while using the biOrb in the past that any food added to the tank tends to hover in the water for a long period of time.  I'm hoping this will fool my new ponies into believing that the cyclops are alive, and they will then eat them.

Hydroids -- These are the bane of a dwarf seahorse-keeper's existence.  They're tiny stinging things that can kill off your entire herd.  The worst part about them is that their favorite food is the dwarf seahorse's favorite food -- baby brine shrimp -- and they can show up in a tank having traveled on brine shrimp eggs!  This is why it is imperative that you either hatch the bbs outside of the tank, or use decapsulated brine shrimp eggs.  Some seahorse keepers insist that you do both.
  -- Anti-Hydroid Medication -- For information on this, please read this book or join the Yahoogroups e-mail group "Ultimate Seahorse."  There have also been reports that Fluke Tabs are effective against hydroids.  Be wary when using anti-hydroid medications, because certain corals, interesting worms (feather dusters and bristleworms) and some copepods may perish after treatment.  I had a sun coral that died gradually over a period of 3 months after I treated my biOrb for hydroids.

Lifespan -- One to two years in captivity, six months to one year in the wild.  The fact that they have short lives in the wild helps explain why they reproduce so often.

Lighting -- Dwarf seahorses are like most other seahorses in that they do not like bright light.  You may have to ramp up the lighting a bit if you are attempting to grow seagrass, but other than that, there is no need to have bright lighting in a seahorse tank.  2 fluorescent watts per gallon will do just fine.

Live Rock -- This is a huge no-no!  All live rock harbors hydroids.  Hydroids can sting your ponies to death.  I assume that in the wild, dwarf seahorses escape this fate because they are in a large body of water and the problem is not so concentrated as it is in an aquarium (also, these seahorses don't eat brine shrimp in the wild, and hydroids go mad over brine shrimp).  Another problem that comes with live rock are equally nasty hitchhikers like bristleworms (which are actually good tank cleaners, but I've heard conflicting reports on how safe they are as tankmates for seahorses), and mantis or pistol shrimp (which will eat dwarf seahorses).  There are lovely live-rock replicas that you can use with your dwarf seahorses; get those instead if you want the live-rock look.  In time these replicas will perform the same helpful function as real live rock.

Some vendors are now carrying seagrass replicas mounted on plastic grids.  These are meant specifically for seahorses and although they are hard to find, it's worth the search.  Try finding them on Ebay.

Refugiums -- Your pony tank is going to be too small for you to worry about a refugium.  As for the question of whether dwarf seahorses can live in the refugium of a large tank, I'd say the answer is no for two reasons: high water flow and intense lighting.  I've heard of advanced seahorse-keepers keeping these little guys in huge tanks alongside much larger seahorses (probably the erectus seahorse, which is found in some of the same habitat as the dwarf seahorse).  Although seahorses will not attack one another, this is best not attempted by beginner or intermediate aquarists because of the problem of ensuring that the dwarf ponies are getting enough to eat.

Size of Dwarf Seahorses -- 1" to 1-1/2".

Substrate -- Marine live sand is fine; aquarium-safe shells work well, too.

Tankmates -- None.  Really, none.  It's easiest.  However, if you really want to have something else in the tank, perhaps a nassarius snail (if you have a sand substrate) would be nice, or a food-source tankmate such as copepods, which you can purchase.  Although it's difficult to locate a source for the tiny asterina starfish (a.k.a. microstars or mini brittle starfish), these also work out quite well with dwarf ponies.  The jury is out on whether blue- or red-leg hermit crabs are okay to have with dwarf seahorses.  Just to be safe I'd say "no," even though I currently own two blueleg crabs who are living with my seahorses, and so far have not noted any problem with the combination.  Do not combine blueleg crabs with redleg crabs if you decide to try keeping crabs, because the redlegs will eat the bluelegs.  No shrimp with seahorses, either, unless they are tiny Hawaiian red shrimp.  Dragonettes have been recommended as tankmates, but these are among the most difficult of saltwater fish to keep and are not recommended for beginners with brand-spanking new marine tanks.  Trust me, your beautiful dragonette will die within weeks and you'll be heartbroken.  Leave the dragonettes for the experts with huge, long-established tanks.  You'll be one of those yourself one day!

Temperature -- Dwarf seahorses can withstand a fairly wide range of temperatures.  However, in the home aquarium, room-temperature or better is suggested.  If you like a very cold house, you'll need a heater to keep the tank above 72 degrees Fahrenheit.  Heaters can be dangerous for seahorses, as they tend to wrap their tails around heaters and burn themselves.  It's best not to use a heater at all and leave the tank at room temperature.  But if you find you need a heater, try to find a plastic heater guard to wrap around it.

Terminology -- Dwarf seahorses are known by the scientific name hippocampus zosterae, and also as "pixies" (caution: this name seems to be registered) and sometimes "pygmy" seahorses.  While the last term is widely used, I disagree with it because six much smaller seahorses, h. debelius, h pontohi, h. severnsi, h. satomiae, h. denise, and h. walea, were recently discovered and given the name "pygmy;" there are also at least one other species, h. bargibanti, that is smaller than the dwarf seahorse, and also shares the title "pygmy."

(As an aside, Hippocampus denise is an almost invisible fish about 1/2" long, making our 1" to 1-1/2" dwarf ponies look rather large in comparison.  H. pontohi, h. severnsi, and h. satomiae are around that size as well, as is h. walea and h. debelius. You cannot purchase any of these tiny seahorses; very little is known about these species as only a few of them have ever been seen.  No doubt they will be protected if they aren't already, and it could be that they are so highly specialized that it would be next to impossible to keep them successfully at home.  To see a video of h. denise, click on this link.  I am unable to locate a video of h. pontohi, but you can see photos here, and photos of h. severnsi and h. satomiae here.  H. walea and h. debelius are absolutely brand-new discoveries as of this writing in February of 2009; there are pictures of them and some of the other recently-discovered pygmy seahorses here.)

Dwarf seahorses are also referred to as "ponies."  As you've seen, I do that a lot on this site.  However, like "pygmy," they share this common name with other seahorses (the slightly larger h. fuscus, the "sea pony," being one of them).  Because of this, "dwarf seahorse" seems to be the most accurate common name for h. zosterae; maybe "pixie" is also a good one, but it is not often used and as I mentioned, may be registered to one person or company.

A group of seahorses is called a "herd" (I often use "colony" here, but that's not really correct), and an aquarium housing them is often referred to as a "corral."  A seahorse that has never seen the sea (one born and raised in an aquarium), is called "tank bred," or more commonly "captive bred."  One that has been wild-caught but taught to eat frozen food is often called "tank raised."  Beware of this term, especially if it is coupled with a low price.  Tank-raised seahorses tend to become untrained (in terms of eating frozen food) very suddenly.  When this happens, you're stuck trying to find live food every day.  For some seahorses this is relatively simple; for others, it is not.

UV Sterilizer -- These probably work well in big tanks, but a dwarf seahorse tank is going to be so tiny that any UV sterilizer is going to cause way too much water flow.  Don't bother with these.

Water Conditions and Tank Cycling  -- Your tank must be cycled!  The water must be squeaky clean, of course, and should test as follows: ammonia 0, nitrite 0, nitrate 0 (or as close to 0 as possible).  The pH should be about 8.2.  Yes, you do need a marine water-testing kit .

You'll also need some sort of gizmo to measure the salinity of the water.  Refractometers are better than hydrometers, but they are expensive.  Hydrometers are cheaper, but less accurate, and some are too large to use with the tiny tanks that house dwarf seahorses.  Decide early about which to get, and get it before you get seahorses.  If all this is alien to you, please research the subjects of aquarium cycling and saltwater before getting seahorses.  The linked page at the end of this sentence, which I wrote to help owners of the freshwater dwarf African frog, is about freshwater aquarium cycling -- but it's still helpful in terms of explaining why aquariums must be cycled and humane ways to do it: http://www.freewebs.com/aquafrog/aquariumcycling.htm.  Once you understand why you must do this, please see this link for specifics on cycling a marine tank:  http://www.freeinfosociety.com/site.php?postnum=813.  Expect this process to take at least six weeks instead of the one month mentioned in the frog site.  Freshwater tanks cycle more quickly.

My main argument with most sites that detail marine tank cycling is that they concentrate on adding "live rock" to the tank, which one cannot do with a tank intended for a dwarf seahorse colony.  You can, however, substitute live sand and bacterial supplements for live rock.  You can also cycle a marine tank without any of this stuff, but it will take a few months and could be a very frustrating process.

Put a strip of tape on the tank to indicate the desired water level.  As the water evaporates, top it off with distilled, reverse osmosis, or deonized water.  Do NOT use tap water -- not even tap water that has been treated to remove chlorine.  It could ruin your tank.

Because little seahorses make a big mess, do a partial (about 10%) water change once a week without fail.  Cleaning the substrate with a vacuum can be a tricky thing to do when baby seahorses are present, but you should do that at least once a month. 

As mentioned previously, bottled seawater is just fine for use in a seahorse aquarium; however, the salinity of this water sometimes tends to be a bit high for dwarf seahorses.  Because of this, you may want to experiment with adding distilled, reverse-osmosis, or deionized water, just enough to bring the salinity down to 1.021 at the most or 1.019 at the least.  If you change the salinity of the water in the tank, do so gradually over the period of a day or so.

Extra-high salinity may cause your ponies to stop doing what comes very naturally to them: breeding.

Dwarf seahorses have been found in brackish estuaries, but don't keep them in this kind of water.  I'm only adding this to point out that these are fairly hardy little creatures who will forgive many of a beginner marine-aquarist's errors.