Re:Sea horse tank ?

#3603
Pete Giwojna
Guest

Dear Lynn:

Thank you for the additional information — it really helps us narrow things down and I now know what type of nursery tank you will need.

A brood of 1500 young is very large, and there are only a few species of seahorses that are able to carry and deliver such an enormous brood of babies. Here in the United States, there are two species — Hippocampus reidi and Hippocampus ingens that are capable of such a feat. Both of these are examples of the greater or "giant" seahorses, but Hippocampus ingens is rarely seen in the hobby whereas Hippocampus reidi is commonly available and extremely popular in the aquarium industry.

It therefore seems quite likely that your seahorses are Hippocampus reidi, commonly known as Brazilian seahorses. I refer to these beautiful seahorses as "Brazilian breeding machines" because they are capable of churning out huge broods of babies every 14 days with clocklike regularity when conditions are favorable.

At any rate, Lynn, it is apparent that you are dealing with seahorses that produce very large numbers of tiny offspring that go through an extended pelagic phase of development. Unfortunately, this makes the babies very difficult to raise and you have done very well to keep three of the newborns alive this long in your first attempt at rearing. For best results with seahorses that used this type of reproductive strategy, you will need to set up a pseudokreisel-type of nursery with a circular flow to help keep the fry away from the surface and you’ll have to provide the newborns with rotifers or larval copepods for the first week or so of their life in order to increase the survivorship of the babies.

Hippocampus reidi are famous among seahorse keepers for two things: brilliant colors and making babies. The Brazilian breeding machine is the most prolific of all the seahorses (Abbott 2003). They have a well-deserved reputation for churning out brood after brood every two weeks with relentless regularity, and hold the world record for delivering ~1600 young in a single brood (anecdotal reports of broods up to 2000 fry are not uncommon)! Not bad for a livebearer. But with that many fetal fry crammed into one incubator pouch, the inevitable tradeoff is that the young are born at a considerably smaller size than most seahorses (Abbott 2003). They also go through a lengthy pelagic phase, drifting freely with the plankton for up to 1-2 months, which makes H. reidi fry notoriously difficult to raise (Abbott 2003).

The phenomenal output of offspring H. reidi produces is a mixed blessing for hobbyists (Giwojna, Jun. 2002). When combined with the promiscuous nature of captive-bred Brazilians, it means their owners are treated to one of the grandest spectacles in all of nature with delightful regularity — the colorful courtship and love dance of the seahorse (Giwojna, Jun. 2002). Brazilians favor particularly brilliant courtship colors, such as hot pink and tangerine, so the opportunity to observe the unparalleled pageantry and charming choreography of their courtship displays so often is a marvelous bonus for aquarists (Giwojna, Jun. 2002).

On the other hand, the short gestation period combined with those huge broods means that the newborn Brazilian fry are smaller and less well developed than most other seahorses (Giwojna, Jun. 2002). Many of them will be too small to accept newly hatched Artemia nauplii as their first food, and the fry undergo a prolonged pelagic phase, during which they drift freely amidst the plankton for the 1-2 months of their lives (Giwojna, Jun. 2002). The pelagic fry tend to gulp air and cling to the surface, making surface huggers and floaters with buoyancy problems a constant threat (Giwojna, Jun. 2002). Survivorship is typically quite low and the entire brood is often lost. Even accomplished breeders often struggle with this species (Giwojna, Jun. 2002).

Unfortunately, your reidi babies are not suitable for the easy rearing method and require the more complicated "food-chain" method of rearing, as described in the following online article, which will also explain why H. reidi fry are harder to raise than others and discuss how to culture live foods for the fry:

Click here: Seahorse.com – Seahorse, Sea Life, Marine Life, Aquafarm Sales, Feeds and Accessories – Nutrition – Feeding & Rear
<http://www.seahorse.com/FAMA_-_Freshwater_and_Marine_Aquarium_magazine/Horse_Forum_-_Nutrition/&gt; Nutrition_-_Feeding_%26_Rearing_the_Fry_-_Part_IV/

Three factors have been found to increase the survivorship of reidi fry during their pelagic phase: (1) the use of kreisel or pseudokreisel nurseries, (2) hyposalinity, and (3) the use of greenwater to maintain the proper level of turbidity in the nurseries and help keep the phototropic fry away from the surface.

Kreisel and Pseudokreisel Nurseries.

Kreisel/pseudokreisel nursery tanks rely on gentle, carefully directed currents to keep pelagic fry — and their food (rotifers, Artemia nauplii, copepods, etc.) — suspended evenly in a circular flow until the young seahorses are ready to settle down on the bottom. Centripetal force draws the fry and their food gently towards the center of this vortex and keeps them suspended in midwater. This has several beneficial effects. Most importantly, it keeps the fry off the surface and prevents them from gulping air. Secondly, it keeps the newborns from swimming into the side glass (in the vastness of the ocean, pelagic fry NEVER encounter such obstacles, and the baffled newborns can injure or exhaust themselves trying to swim through these invisible barriers in an aquarium). And it has the added advantage of concentrating the newborns’ food supply exactly where the hungry fry are drifting.

The kreisel-effect can be accomplished any number of ways, and is generally much easier to achieve than you might imagine. Many different pseudokreisel designs are suitable for use by the home hobbyist, but Liisa Coit’s in-tank nurseries featuring drum-style goldfish bowls as the inner rearing chambers are among the very best.

Hyposalinity for Pelagic Nurseries.

Regardless of the type of nursery tank you use, there is one simple measure you can take to counteract the surface-hugging tendency of pelagic fry and increase survivorship during their pelagic phase: raise them at reduced salinity. Keeping the nurseries at a specific gravity of 1.016 (23 ppt salinity) makes the fry less buoyant and thereby reduces problems with surface huggers, entrapment in surface tension and accidentally ingesting air while feeding at the surface.

As an added benefit, reduced salinity also helps prevent parasite problems. Marine parasites need high osmotic pressure externally in order to maintain a normal water balance within their bodies (Kollman, 1998). Reduce the salinity of the surrounding saltwater sufficiently, and water moves via osmosis into the parasites’ bodies until they literally explode (Kollman, 1998). A specific gravity of 1.016 is low enough to provide the fry with a significant measure of protection from parasites in this way.

Hyposalinity is compatible with all types of nurseries. It can be safely employed with shaded or side-lit nurseries, kreisels and pseudokreisels, or divided nurseries and in-tank nurseries. Hippocampus reidi breeders report that reducing the salinity in their fry tanks can reduce mortalities by up to 50% during the high-risk pelagic period (Nicola Strawbridge, pers. com.).

The Greenwater “Starter” Nursery.

Basically, this system involves giving small numbers of handpicked fry a head start by raising them in a tank with a well-established greenwater culture for the crucial first week or two of their lives. A tank of greenwater is set up in a well-lit area and once the microalgae culture has taken off, it is seeded with copepods or rotifers. The microalgae acts as the filtration, utilizing nitrogenous wastes for growth. The idea is to provide a balanced system in microcosm with a self-sustaining food chain: the phytoplankton (microalgae culture) utilizes sunlight and nitrogenous wastes for growth and helps maintain water quality, while zooplankton (copepods or rotifers) feed on the microalgae and larger predators (seahorse fry) keep the ‘pod population in check. Additional greenwater and/or copepods or rotifers may be added periodically as needed to keep the nursery going.

The turbidity provided by the greenwater helps keep the phototropic fry evenly dispersed throughout the water column and away from the surface. Jorge Gomezjurado has been very successful rearing Hippocampus reidi and H. ingens fry at the National Aquarium in Baltimore using kreisel nurseries with the proper density of microalgae (i.e., greenwater). Jorge has found that turbidity is an important factor in the juvenile rearing environment for these species and he achieves the proper level of murkiness for optimum results by using algae (Nannochloropsis and Isochrysis) at a concentration of about 100 cells per ml (Bull and Mitchell 2002).

Jorge’s Tips.

The following recommendations for nursery and rearing tanks, as well as diet and nutrition, are again based on Jorge Gomezjurado’s successful breeding and rearing program for H. reidi at NAIB.

Jorge notes that the best way to rear reidi fry is by using circular black pseudokreisel nurseries with the flows being established by positioning a bubble curtain or a water jet at one end of the tank (Bull and Mitchell, 2002, p51). He cautions that the stocking density should be limited to no more than 80 fry per gallon (20 fry per liter) for the first two months (Bull and Mitchell, 2002, p51). After the second month, the juveniles will have passed through their pelagic phase and can be transferred to a regular rectangular rearing tank without turbulence or a circular kreisel flow for further growth and development (Bull and Mitchell, 2002, p51).

Water quality and photoperiod should be maintained by using 10% daily water changes and 150-200 Lux as the optimal light level (Bull and Mitchell, 2002, p51). Jorge advises that turbidity is an important factor in the fry’s rearing environment. He uses a technique similar to greenwater nurseries to maintain the proper level of turbidity by adding algae (Nannochloropsis and Isochrysis) at a concentration of about 100 cells per ml (Bull and Mitchell, 2002, p51).

Jorge finds that the optimal water flow for rearing reidi fry 10 mm/sec, and he notes that feeding decreases at lower or higher flow rates (Bull and Mitchell, 2002, p51). At the proper level of flow (10mm/sec), the water movement also generates enough turbulence to break the surface tension of the water, allowing the newborn fry access to the surface where they will gulp enough air to inflate their swim bladders initially and achieve neutral buoyancy (Bull and Mitchell, 2002, p51).

Diet, Nutrition, and Feeding Techniques:

Gomezjurado stresses that high standards of hygiene must be maintained during food preparation and the maintenance of live food cultures. He points that the quality and quantity of the food you provide are important regulators of seahorse growth and survival (Bull and Mitchell, 2002, p51).

Adult H. reidi at the National Aquarium in Baltimore receive a staple diet of frozen mysid shrimp (Mysis relicta) coated with essential vitamins and amino acids, Astaxanthin Natu-Rose, and Canthaxanthin (Bull and Mitchell, 2002, p51). They receive 3 feedings of day of the enriched frozen Mysis relicta, and this highly nutritious diet is one of the keys to their successful breeding and rearing program for H. reidi (Bull and Mitchell, 2002, p51). Jorge Gomezjurado finds that providing his broodstock with a well rounded, nutritious diet increases the size of the fry they produce (Bull and Mitchell, 2002, p51). Consequently, his reidi fry are closer to 10mm in length than the usual 6-7mm (Bull and Mitchell, 2002, p51). The larger reidi are able to feed more efficiently and can ingest larger prey items, including Artemia franciscana Instar I nauplii, thus giving them a considerable advantage over the smaller fry (Bull and Mitchell, 2002, p51).

As with all seahorse fry, Gomezjurado finds that providing H. reidi fry with proper nutrition during the crucial first weeks of life is one of the greatest challenges in seahorse husbandry. He meets that challenge by providing the developing fry with a natural food chain of living prey (Bull and Mitchell, 2002, p51). This live food chain consists of phytoplankton (species such as Nannochloropsis aculata and Isocchrysis galvana), brine shrimp nauplii (Artemia franciscana), copepods (Acartia tonsa), and juvenile Mysis shrimp (Americomysis bahia) (Bull and Mitchell, 2002, p51). The microalgae (phytoplankton) serve as a source of food and nutrition for the various zooplankton in the chain, and the progressively larger prey items are introduced to the fry and juveniles as they grow (Bull and Mitchell, 2002, p51).

The feeding levels provided at NAIB depend on the stocking densities of the nurseries and rearing tanks, which Jorge cautions should not exceed 80 fry per gallon or 20 fry per liter in the case of H. reidi (Bull and Mitchell, 2002, p51). Recommended feeding densities for reidi fry are 10 rotifers/ml, 15 nauplii/ml, and 3 copepods/ml to start with, with the amounts increased accordingly as the fry grow to keep up with demand (Bull and Mitchell, 2002, p51). The water intakes in the rearing tanks are closed or markedly reduced during feeding times. Jorge finds that the gradual transfer from one live food organism to another is easily achieved simply by overlapping feedings at the different weaning stages (Bull and Mitchell, 2002, p51).

The zooplankton that comprise the live food chain at NAIB are enriched with essential vitamins, commercial Highly Unsaturated Fatty Acids (HUFA) rich in docosahexaenoic acid (DHA), and carotenoids such as Astaxanthene biological pigment Natu-Rose (Bull and Mitchell, 2002, p51). Special precautions are taken at NAIB in order to assure that the enriched brine shrimp nauplii (platinum-grade Artemia franciscana cysts) the Aquarium uses are germ free. The decapsulated brine nauplii are kept at high salinity (55-60 ppt) after hatching and the culture water is changed every day in order to prevent bacterial proliferation (Bull and Mitchell, 2002, p51).

Juvenile H. reidi are ready to be weaned onto frozen mysids by the age of 8 weeks. Jorge finds it helpful to leave the frozen mysids unenriched during this initial training period. He feels the juveniles can better recognize the frozen mysids as prey if it free of any enrichment coating (Bull and Mitchell, 2002, p52).

In summation, the ultimate nursery design for home breeders rearing Hippocampus reidi may thus be Liisa Coit’s in-tank nursery setup (or a variation thereof), with the inner drum-style goldfish bowls adjusted to maintain the circular kreisel flow and the optimal turbulence at a rate of 10mm/sec, and the specific gravity adjusted to 1.016 to provide moderate hyposalinity, a 12:12 photoperiod at 150-200 Lux, and greenwater added as necessary to maintain the necessary turbidity (i.e., 100 cells/microliter).

If you contact me off list, Lynn, I will be happy to send you detailed instructions and a schematic diagram showing exactly how to set up a suitable kriesel nursery for H. reidi babies, along with information explaining how to culture the rotifers and/or copepods the newborns need for their first foods. You can reach me at the following e-mail address anytime: [email protected]

best of luck with your prolific ponies and all of their offspring, Lynn!

Respectfully,
Pete Giwojna


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