Re:Hippocampus Hippocampus

Pete Giwojna

Dear Jeannie:

Congratulations on your Hippocampus hippocampus! That’s a species we rarely see on the side of the pond.

It’s a shame that your female has developed buoyancy problems. When that happens with a female seahorse, you can be sure that it is either due to hyperinflation of the swimbladder or to gas building up within her abdominal cavity (internal Gas Bubble Syndrome). This problem can be treated by partially deflating the swimbladder with a hypodermic, or by pressurizing the affected seahorse in a homemade decompression chamber, or by administering Diamox (the tablet form of acetazolamide) orally, providing the seahorses still eating.

If you refer to Don’s post "Sick Seahorse Floating" (see the following link), you will find a detailed discussion that explains these procedures in some depth:,com_joomlaboard/Itemid,218/func,view/id,3505/catid,2/

Hopefully, one of those procedures will be feasible for you and you will be able to restore your female Hippocampus hippocampus to neutral buoyancy again, Jeannie.

Here is some information on H. hippocampus courtesy of Neil Garrick-Maidment from the 2005 Syngnathid Husbandry Manual:

Short-snouted Seahorse, Hippocampus hippocampus
2005 update of 2002 version
Neil Garrick-Maidment (The Seahorse Trust, UK; [email protected]), Robin James
(Sea Life Centre, UK; [email protected])
and Daniel Davies (Underwater World Hastings, UK; [email protected])
Species Description
This European and North African seahorse is commonly referred to as the short-snouted seahorse
as its snout is usually less than a third of the length of its head. It is a relatively small seahorse,
averaging around 8 cm in height. Colors vary from orange through brown and purple to black.
Sometimes they have tiny white dots on their body. Their adult height can range from 7.0-13.0
cm from their head to tail.
Selection and Suitability
These seahorses have been held in public and private aquaria since the early 1900s and are now
frequently found in European collections. Only in recent years have they been successfully kept
for any length of time and breeding still presents some challenges. H. hippocampus have been
bred in captivity, and its young have been raised to adulthood.
Age, Growth, and Reproduction
Male size varies between 7.1-9.9 cm TL (n=7), and female size varies between 5.9-9.7 cm TL
(n=14) (Reina-Hervas 1989). No information on growth or age/size at sexual maturity is
available. The life span in captivity is reported to be 4-5 years.
H. hippocampus reportedly only breeds during the summer months between April and October in
the wild (Lythgoe and Lythgoe 1971; Wheeler 1985; Whitehead 1986; Reina-Hervas 1989).
Gestation length is around 1 month (Lythgoe and Lythgoe 1971; Cabo 1979), and the brood size
in captivity has been reported as being up to 200.
Underwater World (Hastings) reports juvenile size at birth ranges between 5.5-7.5 mm in
length. After one study during which growth was recorded throughout the first month the
juveniles reached an average size of 18.9 mm.
Habitat Parameters
Tank Design Parameters
Population: 2 pairs of adults
Volume of tank: 684 l
Height of tank: at least 45 cm tall
Filtration: undergravel filter and external filtration
Substrate: crushed coral sand
Holdfasts: driftwood is recommended
Lighting: variable to provide bright light and shaded areas
Photoperiod: seasonal variation from 14:8 L:D in summer to 8:14 in winter
Temperature: Summer 19oC, Winter 14oC
N02: 0
pH: 7.9-8.3
Salinity: 35 ppt
Water Changes: 20% weekly
Ideal mates for the tank are hermit crabs and other similar yet non-aggressive species.
Diet, Nutrition and Feeding Techniques
In the wild, the diet of H. hippocampus consists of microinvertebrates, especially
microcrustaceans (Cabo, 1979). The most suitable food in captivity appears to be live mysis
shrimp; however, these may only be available seasonally. Artemia enriched with Selco or
equivalent can be used as a supplementary food but should not be fed exclusively. Frozen mysis
is a commonly used food for adults and are easier to obtain and maintain. A healthy seahorse
should eat up to 30 to 50 mysis shrimp a day. Seahorses should be gradually weaned onto frozen
mysis over the course of 8-10 weeks.
Juvenile feeding regimes
Underwater World (Hastings) feeds juvenile H. hippocampus rotifers and benthic copepods
enriched on a mixture of Isochrysis, Nannochlropsis, Tetraselmsis and Colourfin fishvits. The
rotifers are added at a concentration of 15 rotifers per ml 3 times a day, alongside the rotifers a
diluted solution of the enrichment diet can also be added to the rearing vessel to enable feeding of
the benthic copepods. This is continued until day 28. Newly hatched Artemia naupli are then used
alongside the rotifers and copepods from day 15 to day 60.
Collection Management
This is a priority species for the European Fish and Aquatic Invertebrate TAG. The current
priority is to establish breeding groups at participating institutions and develop husbandry
Cabo, F.L. 1979. Ichtiologia del Mar Menor(Murcia). Secretariado de Publicaciones, Universidad
de Murcia: 143-150.
Garrick-Maidment, Neil. 1994 Seahorses Conservation and care. TFH, Jersey City, New Jersey.
Lythgoe , J. and G. Lythgoe. 1971. Family Syngnathidae. Fishes of the Sea. Blandford Press,
London: 182-187.
Reina -Hervas, J.A. 1989. Contribucion al estudio de la F. Syngnathidae (Pisces) en las costas del
surestede Espana. Arquivos Do Museu Bocage. Nova Serie. I(21):325-334
Wheeler, A. 1985. World encyclopedia of fishes. MacDonald and Co. Ltd. London, UK.
Whitehead, P.J.P., editor. 1986. Fishes of the north-eastern Atlantic and the Mediterranean,
Unesco, Paris.

Best of luck with your short-snouted seahorses, Jeannie.

Pete Giwojna

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