How Big Are Those Seahorses, Anyway?

People often ask about my seahorses–starting with the obvious “why” and branching out from there.

15K16 Feeding

One of the common questions that follows is “How big are they?” (An alternate variation is, “How big is your tank”–the answer is sixty gallons.)

15K16 Reef

There are over 40 species of seahorses, all members of the family Syngnathidae (which includes seahorses, sea dragons, pipefish, and pipe horses) and the genus Hippocampus (which translates “sea-monster horse”).

The smallest seahorses are Pygmy Seahorses, which reach an average size of 0.6-0.8″ (yep, that’s not a typo–the adults are under an inch in length). They can be kept in captivity, but they’re among the most difficult seahorses to keep, because they have extremely special needs, including tanks so small that salinity changes due to evaporation are a serious and constant issue.

On the other end of the spectrum, the Pacific Seahorse can reach an adult length of 12″. These, too, are kept in home aquariums, but require much larger tanks than their tiny counterparts.

About half a dozen seahorse species are commonly seen in home reefs, though only rarely would you see more than one species in the same tank, because seahorses are far more susceptible to disease, and do not thrive as well, when multiple species are housed together.

15K17 Magellan

My seahorses are all captive-bread Hippocampus erectus–aka “Lined seahorse(s)”–a species that averages 7″ in length when mature (and can reach 9″). I originally opted for H. erectus because they’re considered one of the “easy” seahorses–which still doesn’t make them “easy” to care for, but on a comparative seahorse scale they’re on the easy end.

Like most seahorses, H. erectus eats primarily small crustaceans. Mine are trained to a diet of (defrosted) frozen mysis shrimp, which is far more nutritious than the more-familiar brine shrimp. (Brine shrimp are essentially the M&Ms of the sea–tasty, and tempting, but not high on nutritional value.) 

15K16 Moya

My seahorses come from Seahorse Source, a breeder in Florida that raises seahorses in captivity, and doesn’t draw from wild stocks. Many, if not most, of the seahorses seen in pet and aquarium stores are wild caught, which not only depletes an already threatened natural resource, but results in far less healthy specimens than purchasing captive-bred seahorses. (Note: “captive raised” is not the same as captive bred. Captive raised or “tank raised” seahorses may be captured from the wild, as opposed to being entirely bred and raised in captivity.) 

15J13 Moya searching

Seahorses make fascinating pets, but bad additions to standard “community” reef tanks. They’re delicate, and have special feeding needs (tune in next week…) which make them better suited to reefs designed to meet their special needs. That said, they’re certainly not an impossible fish to keep, and they offer a lot more personality and interactivity than a lot of simpler aquarium species.

Do you have, or have you kept, an aquarium? Which aquatic species do you like best?