Re:raising seahorses

Pete Giwojna

Dear brm & kichikoi:

Congratulations on your breeding pairs of ponies! They must feel right at home in the conditions that you have provided for them to have set up housekeeping and mated successfully. Now that they have paired off and begun breeding, you can expect them to produce new broods for you regularly, as long as you provide them with optimal water quality and a nutritious diet. Well done!

Brm, the pelvic crunches, pouch contractions, and pelvic thrusts your male seahorse has been performing may simply be pouch displays (aptly known as Pumping), which are part of the seahorses courtship ritual and a prelude to the actual mating rise. The pumping displays are identical to the contortions that a male seahorse undergoes when giving birth, so you could be witnessing courtship rather than the onset of labor.

But even if you are observing pouch displays rather than the culmination of a successful pregnancy, the Pumping is an indication that your stallion has an active interest in courtship and breeding and is trying his best to get himself pregnant, so if the female is receptive, there will be babies on the way sooner or later…

Brm, the improvised nursery tank you are attempting to set up in which the plastic fish bowl is held in place at the top of the aquarium by positioning it in a net nursery for livebearers, is a variation of the popular in-tank goldfish bowl kriesel nurseries. You are on the right track and the information I provided for you below should help you to get a kriesel-style nursery up and running properly:

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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 thus 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 helps keep 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. For example, one early kreisel-type design employed a small hexagonal aquarium as a nursery. A hex tank generally has the right height-to-circumference ratio to produce good results and the hexagonal sides approximate a circle, giving it the right shape for a kreisel design. To produce the proper flow, an airlift was positioned in the exact center of the tank, with the lift tube extended so it protruded slightly above the level of the water. The airflow was adjusted so that it lifted the water just enough to spill gently over the top of the tube all the way around. The water would well up over the top of the tube, flow down and outward to the sides of the hex, which would then direct it downwards, across the bottom, and back up at the center of the tank, thus creating a gentle toroidal circulation pattern within the tank. The fry and their food would be suspended and concentrated along the central midline of this torus as a result.

A simpler but equally effective pseudokreisel design uses two very small powerheads positioned at the extreme top of the tank on opposite sides to produce the desired circular flow while providing surface agitation and efficient gas exchange. The two pumps create the swirling pseudokreisel effect that breaks up surface tension, eliminates dead spots at top where pelagic fry otherwise tend to accumulate, and keeps surface-huggers from sticking to the sides of the aquarium (Etling, pers. com.). High tanks rather than the long versions work best for this type of nursery, simply because their dimensions (length-to-width ratio) are better suited for producing the circular flow. Karen Etling has used this type of pseudokreisel nursery to raise extremely challenging Hippocampus reidi fry with impressive results.

Sometimes the most effective pseudokreisel nurseries are also the simplest. One such design uses a bubble wand or air bar positioned tightly against one side of the aquarium to disrupt the surface tension and create a slow, circular current. If the tank is rectangular in shape, the bubble wand should be secured at the bottom of one of the long sides of the aquarium. What could be easier?

Aside from its simplicity, the beauty of this system is its versatility. It can be scaled up to whatever size nursery is required or desired. For example, Jorge A. Gomezjurado used this exact type of pseudokreisel for a 90-gallon nursery at the Steinhart Aquarium, where it proved to be very effective for raising huge broods of pelagic Hippocampus ingens fry. Jorge notes the circular current (the kreisel effect) works well for keeping the fry away from to top and keeps the developing young and their food dispersed uniformly through the nursery tank (Gomezjurado, pers. com.).

A variation on this type of nursery adds drip bars or spray bars positioned just above the water level to create additional surface turbulence. When used in conjunction with the back-mounted bubble wand, the spray bars enhance the effectiveness of the circular flow pattern in nudging the fry away from the surface. This combination of surface agitation plus the kreisel effect is very efficient at preventing pelagic fry from getting stuck to the sides and entrapped by surface tension (Bethany Watson, pers. com.).

Another very simple, inexpensive kreisel design 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.

Another very effective kriesel design that is easy to fabricate from readily available materials involves cutting a section from a 5-gallon plastic water bottle, which is then mounted inside either a standard 10 gallon aquarium or a 20 Long tank. The resulting kriesel is similar to the goldfish bowl kriesel nurseries but even larger and sometimes easier to construct. The following website illustrates exactly how to put together a large do-it-yourself kriesel from plastic water bottles using this technique, including step-by-step photographs showing the construction of the nursery. I highly recommend studying this design before you decide which type of nursery is best suited for your particular purposes. There are even several video clips showing the homemade kriesel design in action:

As you can see, there are many different kreisel and pseudokreisel designs, but all such nursery tanks have certain features in common. They all rely on innovative methods that break the surface tension and result in a circular current pattern (the kreisel effect) that keeps the developing fry uniformly suspended in midwater where their food is likewise concentrated. This is very helpful in overcoming many of the difficulties inherent in raising pelagic seahorse fry, and such nurseries have been employed by many home hobbyists with varying degrees of success. It’s a good system and still in widespread use today, but has lately begun to be supplanted by another design with even more flexibility — the in-tank nursery.

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.

Pat Feeback is another home breeder who employs in-tank goldfish bowl kriesel nurseries with good results for raising the ever-challenging Hippocampus reidi fry. Her basic system is very similar to the one used by Lisa Coit, but Pat uses Mag-Floats (i.e., magnets designed for cleaning aquarium glass) to hold the goldfish bowl kriesels at the water line of the host tank, rather than propping them up on egg-crate shelves. This innovation simplifies the procedure and makes it much easier to hold the goldfish bowls in the proper position in a large, tall host aquarium.

Pat has found that a large host tank with well-established filtration produces much better results than smaller host tanks. She started out with the goldfish bowl kriesels mounted in 10-gallon tanks and eventually moved to larger host aquariums, finally finding the best results came from using her 75-gallon seahorse tank to house the in-tank goldfish bowl kriesel nurseries. The larger water volume in the 75-gallon aquarium provides better water quality and stability for the nurseries it houses, and is large enough to accommodate several goldfish bowl kriesels at one time. This has a number of advantages, especially with the prolific H. reidi, which deliver a new brood of young about every two weeks. For one thing, it allows broods of different ages to be maintained in the different goldfish bowl kriesels within the host tank at the same time. As they grow, the H. reidi juveniles are simply transferred from one goldfish bowl kriesel to the next, making room for a new brood in the goldfish bowl that was vacated. When they have grown sufficiently and made it past the pelagic stage of development, the older juveniles in the last goldfish bowl kriesel are transferred out into a separate grow-out tank for further rearing (Feeback, pers. com.).

Another advantage of Pat’s method is that a larger two-gallon goldfish bowl kriesel nursery within the 75-gallon tank can serve as a paternity ward for her pregnant male. Her reidi stallion produces broods with clocklike regularity, making it easy to determine when he is due to deliver. The night before he is due, she transfers the pregnant male to the 2-gallon kriesel paternity ward after lights out, which she finds is less stressful for the seahorse. The next day he will give birth in the goldfish bowl kriesel and is then released back into the main tank with his mate. Since Pat’s 75-gallon seahorse tank serves as the host aquarium for the goldfish bowl kriesels, her H. reidi stallion never has to be removed from the main tank in order to deliver his young. He remains in visual contact with his mate all the while, and can detect her pheromones (and vice versa) throughout his delivery. In short, with this technique, the pregnant male never has to be separated from his mate and transferred to a strange, new environment in which to give birth, making it a very stress-free procedure. No acclimation whatsoever is involved, since the 2-gallon kriesel goldfish bowl paternity tank shares the same water supply as a 75-gallon main tank (Feeback, pers. com.).

Furthermore, when he gives birth, the newborn H. reidi are delivered directly within the goldfish bowl kriesel nursery tank, so they never have to be handled, transferred to a new tank, or acclimated to differ water quality parameters, which makes the entire process very easy on the delicate newborns as well (Feeback, pers. com.).
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Okay, that’s a quick summary of some of the ways of setting up nursery tanks for pelagic seahorse fry. If you contact me off list ([email protected]), I would be happy to provide you with more information and guidelines on rearing seahorse fry, including a schematic diagram showing how to set up the in tank goldfish bowl kriesel nurseries. And if you inform me of what species of seahorse you are raising, I can also provide you with detailed rearing protocols that have been developed for those particular ponies by professional aquaculturists.

Best of luck with your prolific ponies and all of their progeny!

Happy Trails!
Pete Giwojna

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