Re:New tank

Pete Giwojna

Dear Nigel:

Yes, sir — unless you’re cleanup crew was Johnny on the spot and cleaned up almost all of be spilled eggs before you noticed them, then there is a good chance that your male may have received the majority of the eggs and may therefore be pregnant. Hippocampus erectus often produces broods that number in the hundreds, so if you only observed 20-30 dropped eggs, the rest of them are likely nestled safely within your male’s marsupium right now (or nestled unsafely in the stomachs of your sanitation engineers).

An in-depth discussion explaining what really goes into rearing seahorse fry would require a set of thick books comprising many different volumes, and is quite beyond the scope of this simple forum. Suffice it to say that rearing seahorses is a daunting challenge for the home hobbyists that requires maintaining a battery of live food cultures, daily water changes in the nursery tanks, and a brutal feeding regimen that involves providing fresh live food of the right type to the newborns every few hours throughout the day. But I would be happy to provide you with a few more tips that can help increase the survivorship of your H. erectus fry.

As a home breeder with limited time and resources, the first thing you can do to increase your chances of success is to cull the newborns to reduce the brood to manageable proportions.

Culling Newborn Seahorses.

Start the culling process by eliminating any stillborn young (up to 1/3 of the entire spawn are born dead in some cases; Bellomy, 1969). Other newborns will be alive but still attached to their yolk sacs, and some of the fry may have obvious deformities (Giwojna, Jan. 1997). Such pug-nosed ”preemies” and crippled specimens must also be weeded out since their chances for long-term survival are very poor (Giwojna, Jan. 1997).

Next remove all of the undersized individuals. You will notice that the fry in every brood exhibit a range of sizes (Giwojna, Jan. 1997). The largest individuals may be almost twice the length of the smallest of the fry. Such "runts" are at a serious disadvantage compared to their larger siblings primarily because their bigger brethren benefit from increased feeding opportunities (Giwojna, Jan. 1997). Not only can they swallow larger prey, they can swim further with less expenditure of energy (Giwojna, Jan. 1997). This allows them to feed on a greater range of potential prey and to capture food more efficiently than the small fry.

Continue the process of elimination with the goal of selecting only the healthiest, most vigorous young for further rearing (Giwojna, Jan. 1997). The idea is to decide how many fry you can reasonably hope to care for, and then cull mercilessly until you reach that number. It sounds cruel, but the colossal task ahead is going to stretch your time, equipment and patience to the breaking point, and your limited resources must be reserved for the fry that can benefit from them the most (Giwojna, Jan. 1997). The harsh truth is that if you try to save the entire spawn, you will markedly reduce your chances of raising any of them. It’s far better to keep a few well-fed babies in pristine water and perfect health than it is to keep a few hundred malnourished fry under crowded conditions, in water of rapidly deteriorating quality, that are certain to languish and die (Giwojna, Jan. 1997).

The second thing you can do to reduce the mortality rate of your H. erectus fry is to set up one or more kriesel style nurseries for the newborns. Newborn erectus go through a free-swimming planktonic stage for the first few weeks of life, which probably aids in their dispersal in the wild since parturition is often synchronized with the highest tides. The surface hugging behavior of the fry is probably instinctive (the newborns seem to be positively phototropic) and no doubt beneficial in the vastness of the ocean, but it causes nothing but problems in the aquarium, and the erectus breeder must often deal with a potentially lethal logjam as the entire brood clusters at the surface, forming a writhing mass of newborn seahorses, hopelessly tangled together at the top of the tank. The hobbyist must be prepared for the resulting swarms of interlocked fry and should have appropriate nursery tanks ready to receive them as the healthiest of the newborns are carefully disentangled and transferred to their new quarters for rearing.

As with other seahorses that produce large broods of pelagic fry, mortality is typically very high during this early free-swimming phase. Dave Littlehale of the New Jersey State Aquarium reports that one of the biggest problems associated with rearing erectus fry is the frequency with which they become trapped at the surface with excess air in their abdomens (Bull and Mitchell, 2002, p34). To minimize such difficulties, he suggests using kreisel or pseudokreisel designs or placing a sponge filter towards the center back of conventional rectangular aquarium to create the desired circular water flow (i.e., the kreisel effect) (Bull and Mitchell, 2002, p34). He adds that blacking out various portions of the tank and eliminating overhead light may also help by drawing their prey items away from the top, and notes that juveniles born in deeper tanks seem to develop fewer buoyancy problems (Bull and Mitchell, 2002, p34). In short, tall shaded nurseries with side lighting and a gentle kreisel-style water flow should produce good results.

Littlehale describes one such nursery, which has been used effectively to raise H. erectus (Bull and Mitchell, 2002, p33). It is essentially an in-tank nursery design. The nursery setup he recommends features a 7 liter or roughly 2-gallon inner tank measuring 28x16x15 cm connected to a 34-liter (9 gallons) sump (50x33x20 cm) via an overflow (see diagram). Several loops of monofilament line attached to stainless steel weights serve as artificial hitching posts for the seahorse fry. Water is pumped from the sump into the inner nursery tank by a 30-liter per hour (8-gph) submersible pump (p) and overflows back into the sump. A curved screen made from 0.08-mm mesh (m) keeps the delicate fry from being drawn into the overflow box (Bull and Mitchell, 2002, p33). A 50-watt submersible heater (h) in the sump is used to maintain the water temperature in the nursery at 23.8oC (75oF). Biological and mechanical filtration as well as aeration is provided by a small corner filter (f) filled with biologically conditioned dolomite and filter floss (Bull and Mitchell, 2002, p33). An additional airline (a) is placed behind the mesh screen to safely provide extra aeration. 8-12 hours of illumination is provided for all the nurseries using 40-watt cool white fluorescent tubes. For more details on this rearing system, please refer to Scarratt (1995).

For the average aquarist, the in-tank nurseries described below are more practical alternatives that have proven to be equally effective for the home hobbyist. A series of drum-type goldfish bowls serve as the in-tank nurseries and act as pseudokreisels, establishing the crucial circular water flow that keeps the fry and their food suspended in midwater. They are immersed in larger 10-, 20- or 30-gallon tanks (depending on the number of goldfish-bowl kreisels the outer tank must house) on ready-made platforms that support them at exactly the proper height. Liisa Coit, a very successful home breeder who perfected these nurseries, is now raising her fourth generation of homegrown erectus using this system.

Her system is designed around a very simple, inexpensive kreisel design that is based on the drum-style, dime-store goldfish bowl. The proper goldfish bowls for this type of nursery have a circular cross-section with a flat front and back for better viewing. A slow trickle of bubbles running up the middle of one of the curved sides creates a top-to-bottom circular current. This is accomplished by bending a length of rigid airline tubing to conform to the arc of the side and gluing it in place at the proper position — exactly midway, front to back, ending up exactly halfway down the side of the goldfish bowl (Marliave, pers. com.). A gentle bubble stream originating at this point will generate the desired kreisel flow pattern. (Bending the flexible tubing to the correct curve or arc is the only tricky part about this design. Flexible airline might work just as well, IF you glue it in place securely so it doesn’t work loose.) Silicone aquarium cement is used to fill in the depression around the inside base, a feature common to all such goldfish bowls, in order to prevent debris from accumulating in this groove (Marliave, pers. com.).

Voila — just like that you have a fully functional, room temperature, static kreisel for raising pelagic seahorse fry! This design was developed by Jeff Marliave at the Vancouver Aquarium Marine Science Centre for conducting experiments with nutrition and diet in seahorse husbandry. These goldfish-bowl nurseries are ideal for this since they allow small kreisel setups to be created easily and economically in quantity, which makes it practical to run multiple kreisel nurseries for replicates testing different experimental treatments (Marliave, pers. com.). Hobbyists will find them equally useful for breaking up large broods into manageable groups dispersed among a number of small nurseries.

A suitable hitching post is secured to bottom, precisely in the middle where it won’t disrupt the circular kreisel flow (Marliave, pers. com.). Jeff finds a piece of hard coral tied to a length of unraveled polypropylene twine works well as a central hitching post. This arrangement allows benthic babies, or juvenile pelagic ponies that have settled, to hitch in the calm space at the center of rotation where there food is concentrated by the currents and an endless parade of perfect prey passes right past their snouts (Marliave, pers. com.). This helps maintain the optimal feeding density and provides maximum feeding opportunities for the rapidly growing young with minimum expenditure of energy on their part. They can eat like little pigs all day long at their leisure without any danger of accidentally ingesting air.

The goldfish-bowl kreisels are also easy to keep clean and to sterilize after use. For proper hygiene and sanitation, Jeff recommends washing them out regularly and air drying them, using spare kreisels to replace the rearing tanks in the meantime. Fecal pellets and dead prey items accumulate under the coral for easy siphoning during daily partial water changes, which maintain water quality in the nurseries (Marliave, pers. com.).

One of the few shortcomings of such goldfish-bowl kreisels is that relatively few fry or juveniles can be raised in each bowl due to the small size of the nursery. This is easily compensated for by the fact that it’s simple to set up and operate many such nurseries simultaneously.

In Liisa Coit’s system, the goldfish-bowl kriesels are placed inside larger rectangular aquaria, thus creating in-tank, kriesel-style nurseries, as explained in greater detail below:

The Divided Nursery.

The versatile in-tank nurseries evolved from the basic Divided Nursery tank design, which simply involves separating a standard 10-, 20- or 30-gallon aquarium into two or more different compartments with a common water supply using perforated tank dividers. All of the equipment and filtration goes into one of the resulting compartments while the other compartment(s) serve as the nursery or nurseries for the fry. The perforated barrier allows water to circulate freely between the compartments while acting as a baffle that greatly dampens the turbulence generated on the equipment side.

It is also very effective at keeping newly hatched brine shrimp confined to the fry’s nursery compartment, especially if two of the perforated plastic dividers are positioned side-by-side with a small 1/8-1/4-inch gap between them, forming a double barrier (Abbott, 2003). Sometimes the perforations are covered with plastic window screen or the plastic mesh sold in craft stores for needlepoint projects to increase the effectiveness of the barriers (Abbott, 2003). Many hobbyists also darken the equipment side and position a strip reflector or table lamp at the end of the nursery compartment opposite the filtration side, in order to draw the baby brine shrimp (bbs) away from the tank divider and filters, while concentrating the bbs in a smaller area so the fry can feed more efficiently (Abbott, 2003).

All of the gear is thus isolated on one side of the partition safely away from the fry and their food. The larger volume of water a divided tank provides gives the nursery greater stability as far as fluctuations in temperature and pH go, makes it easier to maintain optimum water quality, and increases your margin for error accordingly (Abbott, 2003). With the tank divided in this way, any sort of mechanical, chemical or biological filtration you care to provide can be safely operated in the equipment area without disturbing the delicate fry in the nursery area (Abbott, 2003). The developing young thus enjoy all the benefits that better filtration and a large water volume can provide, while being confined in a smaller nursery compartment, making it easy to maintain an adequate feeding density (Abbott, 2003).

The divided nursery has proven to be a successful design and hobbyist have developed many variations on this basic theme over the years. In fact, the divided nursery tank was the inspiration for the popular tank-within-a-tank nurseries that were soon to follow.

The In-Tank Nursery.

In-tank nurseries enjoy all the advantages of divided nurseries and then some. For example, like divided nurseries, the tank-within-a-tank design makes it much easier to provide seahorse fry with stable conditions and optimum water quality, vastly increases filtration and equipment options, simplifies maintenance and offers enormous versatility. The idea behind the in-tank nursery is to confine the seahorse fry in a small, flow-through enclosure that can then be attached securely inside a larger aquarium. The in-tank fry enclosure must allow water to pass through it freely but not fry food such as copepods, rotifers or Artemia nauplii. The enclosure thus allows the food to be concentrated in a small space to maintain the proper feeding density, while at the same time providing the fry with all the benefits of living in a much larger volume of water. This includes greater stability in terms of water temp, pH, oxygen levels, salinity and so on.

But by far the biggest advantage of the in-tank nursery is the superior water quality it provides. The larger tanks that accommodate the fry enclosures are normally in the 10-20 gallon range, but there is no upper limit to the size of the host aquarium — the bigger, the better. Of course, for starters, the larger volume of water is naturally more resistant to pollution from the mass consumption and elimination one must deal with when rearing seahorse fry. But more importantly, with the fry safely sheltered in their nursery, the main tank can be equipped with any kind of filtration and filter media you can think of to improve water quality or safeguard the health of the fry. This includes heaters, sponge filters, inside box filters or external power filters with activated carbon, polyfilter pads, or ion-exchange resins, micron-level mechanical filtration, bio-wheels, wet/dry filtration, protein skimmers, UV sterilizers, ozonizers — you name it. Airstones, bubble wands, powerheads, filters and the like can operated full blast without worrying that they’ll buffet the fragile fry or that they filters may ‘eat’ the newborns or consume all their food. Use your imagination — anything goes!

Water quality benefits as a result, and the added filtration reduces the need for frequent water changes. When substantial water changes are called for, the main tank makes the whole process easier.

The first in-tank nurseries were ready-made breeder nets intended for livebearing freshwater tropicals (Abbott, 2003). These breeder nets worked very well for dwarf seahorses, which produce small numbers of babies (Abbott, 2003), but they are not well suited for the huge broods of fry many of the greater seahorses produce. Hobbyists soon began to improvise in order to overcome the limitations of such breeder nets and accommodate larger broods in their fry enclosures. Breeders began to experiment with in-tank refugia, "critter keepers," and various plastic containers to meet their needs. They modified these by drilling them full of holes and covering the holes with plastic mesh. If necessary, an airline is added to the fry enclosure for better circulation and a drip line brings filtered water in from the main tank or an external power filter.

The versatility of in-tank nurseries is one of their biggest assets. They allow almost any existing aquarium to "host" a fry enclosure and there is also great flexibility in the design of the inner nursery tank. They can easily be modified to accommodate either benthic or pelagic seahorse fry, and multiple in-tank nurseries can be housed in one big main aquarium. Endless variations on this basic concept are possible. The in-tank nursery is simply a much more versatile and adaptable design than the divided nurseries that preceded it.

Liisa Coit is one of the innovative aquarists who have experimented with several different in-tank nursery designs. She is a successful private breeder whom has closed the life cycle with Hippocampus erectus and H. zosterae. Liisa is also an accomplished do-it-yourselfer, and she has raised fourth-generation homegrown erectus in a very efficient nursery that combines the benefits of the best static kreisels with the advantages of in-tank nurseries (Coit, pers. com.).

She uses the plastic drum-style goldfish bowls as the fry enclosures. As with the usual goldfish bowl kreisels, a slow trickle of bubbles running up the middle of one of the curved sides creates the desired top-to-bottom circular current (Coit, pers. com.). This is accomplished by drilling a small hole through the side of the plastic bowl at the proper position — exactly midway, front to back, and precisely halfway down the side of the goldfish bowl. A plastic airline tube connector is glued into the bowl though this hole and plastic airline hosing is attached to the outside from an air pump, allowing a gentle stream of air bubbles to be pumped into the goldfish bowl at that point (Coit, pers. com.). This aerates the bowl and establishes the circular flow (i.e., the kreisel effect). The bubble stream is adjusted so it produces a smooth, gently rotation that keeps the fry suspended evenly at the center of the vortex (Coit, pers. com.).

The plastic goldfish bowls are further modified by drilling 1-1/2" holes near the top, which are then covered with silk screen mesh that is glued over them (Coit, pers. com.). This allows the goldfish-bowl kreisels to be submerged up to the rim within a much larger aquarium, an innovation first built and implemented by David Mulcahy. Liisa find that this design is easier to make and accomplishes the same result as the completely submerged "critter keeper" she originally used as her in-tank fry enclosure.

The goldfish-bowl kreisel nurseries are supported on a shelf that runs the length of the host aquarium they are submerged in (Coit, pers. com.). The shelf is very easy to construct from three pieces of plastic "egg crate" light diffuser, which simply snap together (no glue needed). First the shelf itself is cut to the right length. It should be wide enough to accommodate the goldfish bowls and as long as the host aquarium. Next the two legs are cut to support the shelf. The legs should cut to whatever height is needed to raise the goldfish bowls to the desired water level. The bottom of each leg should be smooth but the ridges should be left on the top of each leg. The long shelf can then be placed on top the legs and the ridges will snap in place (Coit, pers. com.). The entire shelf and the goldfish bowls it supports can be pushed back and forth when performing water changes or cleaning the host tank (Coit, pers. com.). For further stability, plastic electrical ties can be used to fasten the legs to the shelf (Coit, pers. com.).

As with any other in-tank nursery, the large host tank can be equipped with whatever supplemental filtration you desire in order to provide optimum water quality to the fry enclosures. This can include a protein skimmer, ultraviolet sterilizer, or external power filter equipped with bio-balls, polyfilter pads, ammonia absorbers, and the like.

Lengths of airline tubing are used to siphon filtered water from the power filter into each of the goldfish-bowl kreisels (Coit, pers. com.). (Since the goldfish bowls are lower that the level of the water in the external filter, gravity keeps the siphons flowing.)

At feeding time, the siphon tubes feeding filtered water to the bowls are removed so they don’t force the brine shrimp nauplii out through the mesh-covered holes (Coit, pers. com.). This assures that a good feeding density of baby brine shrimp is maintained, concentrated with the fry at the center of the bowl and held in suspension by the circular flow. After the fry have had their fill, the water lines are put back in place and soon flush the excess, uneaten Artemia out of the bowls into the main tank, which facilitates the cleaning of the fry enclosures (Coit, pers. com.).

Coit prefers to keep pelagic fry in the goldfish-bowl, in-tank kreisel nurseries until they begin to hitch and orient themselves toward the bottom. At that point, she transfers them into more spacious "critter keeper" in-tank nurseries for further rearing, and finally into 10-gallon grow-out tanks (Coit, pers. com.). As one example of the versatility of in-tank nurseries, the large host aquariums can do double duty as grow-out tanks for the juveniles as long as all of the filter intakes are screened off.

Those are the type of nursery tanks and rearing system you should emulate for best results with your pelagic erectus fry, Nigel. As you can see, the in-tank, goldfish-bowl style nurseries provide all of the advantages of the divided nursery you have in mind plus the added benefit of the circular kriesel flow to help keep the newborns away from the surface. Breaking your main tank into a separate nursery tank and a display tank for the adults using a perforated tank divider wouldn’t be nearly as effective and would subject the parents to increase risk of disease by making the water quality much more difficult to maintain.

Nor would providing your erectus fry with rotifers as their first food be very beneficial. Rotifers can increase the survival rate of newborn seahorses that are too small to accept newly-hatched brine shrimp (Artemia nauplii) as their first food, but that’s not the case with Hippocampus erectus. Mustang and Sunburst babies have no difficulty swallowing newly-hatched brine shrimp right from birth, so offering them rotifers is an unnecessary complication. It won’t make much of a difference, if any, to their overall survival rates.

If rearing is your primary goal, Nigel, then you may want to rethink your plans to of obtain a pair of Hippocampus reidi for that purpose. You could hardly have chosen a more difficult seahorse to raise than H. reidi, sir.

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 professional aquaculturists and accomplished breeders often struggle with this species (Giwojna, Jun. 2002).

If you still want to give raising Brazilian seahorses (H. reidi) a try, be prepared to set them up in specially designed kriesel nurseries and feed them rotifers for the first week or two, as discussed below:

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 the National Aquarium in Baltimore.

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 is10 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).

Best of luck rearing your seahorse fry, Nigel! Don’t be discouraged if you have poor results with your first few attempts at rearing. Once your seahorses begin breeding, you can expect them to provide you with a new brood every month or so during the breeding season, so you’ll have plenty of opportunities to refine your rearing techniques, and as you gain experience, your results will improve.

Happy Trails!
Pete Giwojna

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