Dear Tom:

Pete Giwojna

Dear Tom:

Sure, I would be happy to help you regarding the temperature requirements for Ocean Rider Gigantes (Hippocampus ingens), Tom.

For starters, let me just say that the well-meaning but misguided posters on the reef sites you mentioned are quite incorrect in that regard. They are either basing their criticisms on outdated information or are confusing Ocean Rider’s multigenerational strain of Hippocampus ingens, marketed under the trademark name of “Gigantes,” with the inferior Mexican strain of Hippocampus ingens that were once provided by Eliezer Zuniga, or both.

I must point out that the original ingens broodstock for the Gigantes came from the tropics and are NOT related to Zuniga’s Mexican ingens. Ocean Rider Hippocampus ingens (Gigantes) are born and raised at a constant water temperature of 75°F at the Ocean Rider aquacultural facility in Hawaii, as were their parents and grandparents and great-grandparents before them, and so on and so on, going back for many generations now.

If that’s not enough to persuade them, sir, then simply refer them to “Syngnathid Husbandly in Public Aquariums,” which states that the optimal aquarium water temperature for Hippocampus ingens is 23oC (73oF-74oF). Make sure they understand that the temperature recommendation in the husbandry manual comes from Jorge Gomezjurado (former Head Curator at the National Aquarium in Baltimore and former owner/operator of the Draco Marine aquaculture facility), and is based on the successful rearing program for Hippocampus ingens which Jorge conducted at both of those sites:

Koldewey, Heather, ed. 2005. Syngnathid Husbandry in Public Aquariums: Project Seahorse 2005 Manual (with chapters contributed by members of the Syngnathidae discussion group). Zoological Society of London, Regent’s Park, London NW1 4RY, UK.

Finally, feel free to post the following information, which discusses the temperature requirements for ingens in more detail and explain that it’s a brief excerpt on Hippocampus ingen from Pete Giwojna’s new book on seahorses (unpublished):

Hippocampus ingens are true giants among the seahorses. They have been reported to reach a length of 36 cm or more than 14 inches when fully grown, making them the world’s largest seahorses, rivaled only by the biggest examples of H. abdominalis. The prehensile tail of a large adult has a powerful grip like an anaconda, and they can exert enough pressure to leave you counting your fingers afterwards when they squeeze down.

But despite their great size and power, these gentle giants are not at all the brutes you might imagine. As Alisa Abbott points out, they are close relatives of the Brazilian seahorse (H. reidi), and share their slender profile and graceful proportions (Abbott 2003). Imagine a seahorse with the same sleek silhouette as reidi, but which reaches twice their size, and you will have a pretty good picture of what H. ingens is like (Abbott 2003). They are stately steeds, built like thoroughbred racehorses, which carry their size very well. The crowning touch for the King of all the seahorses is a tall, backward-swept, five-pointed coronet, which adds to their majestic appearance (Abbott 2003). They have very prominent eye spines but are otherwise relatively smooth bodied with small blunt spines.

DNA comparisons using molecular markers (cytochrome b gene sequences from mitochondrial DNA) show that the closest relative of the eastern Pacific seahorse (H. ingens) is none other than the Brazilian seahorse (H. reidi) from the western Atlantic (Dames 2000). It’s believed that the Brazilians and ingens evolved from a single ancestral species beginning about 3 million years ago when the Isthmus of Panama was first formed (Dames 2000), forever dividing their common ancestors into an Atlantic population and a Pacific population. Over the next 3 million years, the Atlantic population developed into the ever-popular Brazilian seahorses (H. reidi), while the Pacific population continued to diverge into the gigantic H. ingens (Giwojna, Jun. 2002). The two species are still closely tied in terms of their reproductive strategy. Both species produce enormous broods (up to 2000) of tiny fry (6-7 mm long) after a short gestation period (14-15 days), leaving the fry with a prolonged pelagic phase in which to complete their early growth and development (Giwojna, Jun. 2002).

There seems to be considerable confusion regarding the temperature requirements of H. ingens. In the literature, you will often see them described as subtropical or even temperate seahorses, but the literature is quite mistaken on this point. They are truly a tropical species whose range extends into subtropical regions in some areas and occasional carries it into temperate areas such as San Diego when El Nino conditions push warm water currents unusually far north (Hubbs and Hinton 1963; Soto 1985).

Carol Cozzi-Schmarr, of the Ocean Rider seahorse farm in Hawaii, is very familiar with H. ingens, going all the way back to her days culturing High Health shrimp in the tropics, which extend from 7º to 23ºN and 7º to 23ºS. The seahorses in these regions were attracted to the shrimping grounds to feed on the larval crustaceans and suffered heavy losses to shrimp trawlers. In fact, it was that experience that first got her and Craig thinking about culturing High Health seahorses rather that shrimp. Here’s what Carol has to say about the temperature requirements of H. ingens (Carol Cozzi-Schmarr, Sep. 2002):

“The Pacific Sea horse (Gigante) is a very beautiful and majestic seahorse indeed! I can see why you would want to add a pair to your tank. I can also see why you are confused about their temperature requirements. Let’s take a look at their natural home ranges and the corresponding ocean temperatures from which the come. This will help you to see that this sea horse is a truly tropical and highly social species!

Their geographic range extends from the coastal waters as far North as San Diego during El Nino years and as far South as the Galapagos and northern Peru. Peru is slightly south of the equator whereas the Galapagos and Ecuador straddle the equator!! The ocean temperature here averages from 80F to 82F! The H. ingens’ range then extends from here up the coast along the Pacific side passing by the Western coast of Columbia (approximately 1-7 degrees latitude), Panama (approximately 7 degrees latitude), Costa Rica (approximately 8-10 degrees latitude), Nicaragua (approximately 10 degrees latitude), El Salvador (approximately 10 degrees latitude), Honduras (approximately 10 degrees latitude) and Guatemala (approximately 14-15 degrees latitude). This whole area has some of the warmest ocean waters on the planet. Warm equatorial currents flow here all year around with the average ocean coastal temperatures being between 82°F and 84°F and increasing to as high as 90°F during the summer (our winter)!! All very hot places with bathtub like ocean temperatures.

This is the main range of this species with coastal waters also being a very, very rich nursery area for Penaeid Shrimp larvae! In fact, the H. ingens (like many sea horses around the world) is a bycatch brought up by local fisherman trawling for shrimp in mostly small wooden pongas (canoe-like boats) but also in larger commercial trawlers. At one time these sea horses were so plentiful and so easy to collect that millions of H ingens were heavily harvested annually for the Chinese medicine market. Now, of course there just are not that many left.

The range now extends into Mexico with a latitude between15-20 degrees. These coastal areas are more familiar to most North Amercians from the large tourism industry. The waters here are still very warm most of the year but do start to cool during the winter with typical ranges being from 72°F to 80°F. Now we reach Baja California and San Diego (30-32 degrees latitude) where H. ingens has been occasionally seen during the El Nino years. Normally the average temperature of San Diego is a chilling range of 55°F to 65°F (13°C-18.5°C) with the warmer temperatures lasting a few brief months in August and September. During El Nino years the warmer currents that originate off equatorial Ecuador push further north than normal, bringing the high temp up to as high as 72°F to 75°F (22°C-24°C)!! This happens on the average once every 4 years. It is during these brief moments that the Pacific Sea Horse has been seen in southern California. There may even have been and occasional sighting further North but this is not their typical home range.

Now it is true that sea horses have an amazing ability to adapt to temperatures different from their native waters, although that may affect their color, activity level and general health and longevity. The Pacific Sea horse (and many other species as well) is one that has adapted fine to these cooler temperatures.

The reason that many Public Aquariums use cooler water is simple…it costs a lot of money to heat saltwater especially when using high volumes like most Aquariums do. If the species in question can adapt well to cooler temperatures and it does not adversely affect the health of the animal this is not a problem. It saves the aquarium a lot of money.

Most Aquariums around the world are located in temperate areas where the ambient ocean temperature from which they pump their water is around 50°F to 55°F (10°C-13°C) or cooler!! They just cannot afford to heat water at all or any more than absolutely necessary. Adjusting the temperature in any way different from the ambient sea from which they pump their seawater if they are lucky enough to be on the coast is an expensive proposition. If they are located far away from the coast and must make their own seawater the cost of heating is an extra expense that adds to an already highly costly recirculation process.

For the home aquarist the situation is the reverse. It is extremely expensive for the hobbyist to cool seawater. It is least expensive to keep your tank at your house ambient temperature, which for most of us is about 75°F or to heat a little bit up to 78°F with a simple heater during the winter months.

So you can put the Pacific Sea Horse in a cooler tank (60°F-65°F) with a chiller if you want to after a very, very careful and slow acclimation but it is not their ideal temperature as they are not temperate fish. You will not see their magical colors and they will be much less active than normal. These Gigante sea horses are true tropical dwellers! Not only do they like it warm but they have big appetites and they are very social!! You will see beautiful tropical colors and a truly happy and active sea horse if you can keep them in herds and at temperatures from 75°F to 80°F (24°C-26.5°C)!! There is no need for a chiller, that is for sure!! Aloha, Carol”
(Carol Cozzi-Schmarr, Sep. 2002)

All things considered, Tom, I would say the comfort range for H. ingens in the home hobby tank falls between 72°F-78ºF (22°C-25ºC), with 74°F-76ºF (23°C-24ºC) being optimal. Suffice it to say that the multigenerational, captive-bred-and-raised H. ingens from Hawaii, marketed as Gigantes, are raised at a constant 75ºF (24ºC) and that is the temperature the ingens keeper should aim to achieve. In your case, sir, I would say that your Gigantes should thrive at a temperature range of 72°F-74°F, so it sounds like your seahorse setup is in great shape when it comes to the water temperature, Tom.

Just remember that aquarium temperatures for this species must be kept below 84°F-86ºF (29°C-30ºC), which can cause fatal heat stress in H. ingens (Eliezer Zúñiga, pers. comm.). Likewise, temperatures below 68ºF (20ºC) should be avoided because the activity of ingens slows to a standstill at such cool temperatures (Eliezer Zúñiga, pers. comm.)

Best wishes with all your fishes, Tom!

Pete Giwojna, Ocean Rider Tech Support.

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