Breeding Seahorses

Dear Dee:

Many temperate and subtemperate seahorses engage in a type of pouch display known as “Ballooning” when they are actively courting, Dee. This is a simple display in which the males inflate their brood pouches to the fullest possible extent and parade around in front of the female in all their glory as though trying to impress her with the sheer dimensions of their pouches. The pumped up paramours perform proudly, putting on quite a show for the flirtatious fillies. (All you ladies out there are surely all too familiar with this act. No doubt you attract the same sort of attention and elicit the same type of behavior every summer at muscle beach, where all the macho men pump up their biceps, suck in their guts, and throw out their chests whenever you stroll past.)

So it sounds like you’re stallion with the rotund pouch is either already pregnant or trying hard to get pregnant by attracting the attention of one of your females with is pouch displays. Either way, Dee, chances are good that you will soon be dueling with a brood of babies.

Yes, a breeder net or net cage can be used as a nursery tank for pelagic seahorse fry in a pinch. Such setups are commonly known as in-tank nurseries, and they can be quite effective as long as you keep them scrupulously clean, as discussed below:

The breeder net should work fine — I know several hobbyists who use them for rearing dwarf seahorse fry. They tend to get a bit dirtier than bare-bottomed nurseries (uneaten brine shrimp and fecal pellets will accumulate on the netting and cling to the mesh) so you’ll need to be diligent about siphoning the netting clean of such wastes and debris, just as you would be when cleaning the glass of a bare-bottomed nursery.

Many hobbyists who used these breeder nets for rearing fry keep two of the nets, one which is in use as a nursery, and a clean spare which they transfer the fry into when the breeder net that’s currently in use gets too dirty despite the siphoning. The dirty net is then cleaned and disinfected thoroughly and held in reserve until the other breeder net needs to be replaced. The two breeder nets are then switched back and forth as often as necessary to assure that the seahorse fry are always contained within a reasonably clean enclosure.

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). I know several hobbyists who use breeder nets for rearing dwarf seahorse fry. They tend to get a bit dirtier than bare-bottomed nurseries (uneaten brine shrimp and fecal pellets will accumulate on the netting and cling to the mesh) so you’ll need to be diligent about siphoning the netting clean of such wastes and debris, just as you would be when cleaning the glass of a bare-bottome nursery. The dirty water should be replaced with cleaned, newly mixed saltwater you’ve prepared and aged/aerated overnight. These small water changes will help maintain good water quality in the nursery.

Many hobbyists who used these breeder nets for rearing fry keep two of the nets, one which is in use as a nursery, and a clean spare which they transfer the fry into when the breeder net that’s currently in use gets too dirty despite the siphoning. The dirty net is then cleaned and disinfected thoroughly and held in reserve until the other breeder net needs to be replaced. The two breeder nets are then switched back and forth as often as necessary to assure that fry are always contained within a reasonably clean enclosure.

These breeder nets worked very well for dwarf seahorses, which produce small numbers of babies (Abbott, 2003), but they are not as 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.

So feel free to keep this unexpected brood of babies in the net cage temporarily for now, as long as you are very careful to keep them scrupulously clean, Dee. Remember, like all babies, seahorse fry exist only to eat and poop.

To say they are voracious is a gross understatement — at this stage of their development, the newborns have but one mission in life: to eat and thus to grow. Researchers have found that a single seahorse only a few weeks old can consume 3000-4000 newly hatched brine shrimp in a single day! Milligram for milligram, a great white shark’s feeding habits appear downright dainty and positively anorexic compared to a baby seahorse on the prowl for live prey. And as you can imagine, when well-fed fry eat that much, defecation is amazingly rapid, with each newborn producing an average of one fecal pellet every 25-30 minutes.

When the time comes, you will probably have several dozen gluttonous Hippocampus erectus fry in your net cage or nursery, each adding its own fecal pellets to that total at the same alarming pace. You really have to stay on top of the sanitation when this sort of wholesale, assembly-line defecation is taking place in a small nursery enclosure.

After a week or so, you will still no doubt need to transfer the fry into a clean fishnet breeder so the old can be removed, cleaned and disinfected thoroughly, and used again when it’s time to move the fry into more sanitary surroundings next time.

When transferring the fry, scoop them up in a small measuring cup or something similar along with a little water. It’s important that the newborns aren’t exposed to the air during the transfers. Or a plastic turkey baster works well for delicately sucking up the fry when transferring them, providing you cut off a bit from the tip of the baster to enlarge the opening at the tip.

Okay, Dee, those are some quick tips regarding the type of improvise nursery tank you are using now. I will send you a separate e-mail with a lot more information on rearing newborn seahorses that includes a lot of other nursery tank designs you can consider for the long-term maintenance of the newborns.

Good luck!

Respectfully,
Pete Giwojna, Ocean Rider Tech Support