Re:Raising ponies … without a special tank

Pete Giwojna

Dear Don:

Yes, sir, Sunbursts are indeed Hippocampus erectus. Congratulations on your new brood of fry!

A refugium teeming with pods is certainly worth a try for anyone who is dealing with a brood of fry and is not set up for rearing but nevertheless wants to give the newborns a chance, however slender that may be. The natural food of seahorse fry in the ocean is zooplankton, and research suggests that the bulk of this consists of larval copepods for many seahorse species.

The sort of simplified rearing system you’re contemplating is usually known as a "natural nursery," as described below, Don:

<Open quote>
The Natural Nursery.

This is a very small-scale, low-maintenance rearing system sometimes employed by harried home hobbyists who are too busy for the brutal feeding regimen and maintenance schedule most other nurseries require. Natural nurseries rely on lots of live rock for biofiltration and are usually set up more or less as a refugium would be. That means lots of macroalgae to provide natural filtration and no predators of any sort, which allows thriving populations of copepods, amphipods and other microfauna to build up over time. The idea is that the overworked aquarist can simply cull through his seahorse’s latest brood, release the hardiest of the newborns in the natural nursery, and allow them to fend for themselves. Sometimes a netful of newly hatched brine shrimp is added now and then to supplement the natural microfauna on which the fry survive, but this is done sporadically at best to stave off the appearance of hydroids and Aiptasia anemones that might otherwise rapidly take over the nursery. The natural filtration provided by the live rock and beds of macroalgae reduces the need for water changes to a minimum and feeding is drastically curtailed compared to other types of nurseries.

As you might expect, most of the fry are lost during the first week or two with this method, but some may manage to find enough natural fodder to survive and it’s not uncommon for a few of them to thrive on their own. That’s all the hobbyist is hoping for with this system and such meager survivorship is considered a victory, since the only alternative in many cases is to sacrifice the entire brood without attempting any rearing whatsoever.

This method of rearing is most successful when the natural nursery/refugium is large and the number of fry it is asked to support is small. For instance, Liisa Coit has used a 5-foot seagrass refugium this way quite successfully when rearing dwarf seahorses (Coit, pers. com.). It is best suited for raising benthic seahorse fry but is also worth a try for raising pelagic fry when there is no other alternative. <Close quote>

So attempting to rearing seahorse fry as you describe will result in very high mortalities, but it is far from hopeless, and it is not uncommon for one or two of the fry to hang in there against all odds and find enough natural fodder to grow and prosper. For example, Heather Hall maintained a rearing program for Hippocampus capensis at the London Zoo that was proving to be too successful, prompting a change in their rearing protocol. In order to keep from being overrun with captive-bred capensis, the Zoo was forced to resort to unusual methods to reduce the reproductive rate of their colony. She describes her experience raising these bountiful breeders as follows: "H. capensis is a relatively prolific species. Brood sizes average about 50 babies… Since survival rate is high with good husbandry and diet, it is easy to become overpopulated with animals. In order to avoid overpopulation we have tried different ways of managing the population in our collection. Separating the sexes was employed in several tanks. Sexes were kept isolated in groups of 20. We found that this led to many problems. The animals exhibited a number of stress signs: disease outbreaks increased and aggression was high between males. Females became swollen with eggs and suspected egg binding occurred. Respiration rates and twitching also increased. Therefore, we decided to separate the sexes of our seahorses no longer. Animals in the display tank are allowed to reproduce as normal, and young are only removed when required. Some young survive in the display tank, feeding on naturally available foods and make it to adulthood. To keep the generations turning over, we can remove up to 20 individuals and raise them in the holding tanks. They can be given special attention there and their growth monitored. This method has worked well for us" (Bull and Mitchell, 2002, p30).

In the end, H. capensis fry at the London Zoo were simply left to their own resources in the display tank with their parents, yet some of them routinely survived to adulthood on their own with no special care whatsoever. Those are benthic babies and the situation is a little different with your Sunburst fry, but certainly worth a try, Don.

Now that your Sunbursts have begun breeding for you, they made produce a new breed every month. Nigel is correct when it comes to transferring the fry from your main tank into the refugium, Don. You must be very careful when transferring the babies into your nursery tank. For future reference, never lift the newborns out the water when transferring them. They will swallow air and may develop fatal buoyancy problems that leave them bobbing helplessly at the surface, unable to submerge or eat (Giwojna, Jan. 1997). Netting them out or otherwise exposing the newborns to the air is one of the most common mistakes inexperienced breeders make, and it often results in the loss of the entire brood (Giwojna, Jan. 1997). The proper way to move the babies is to carefully scoop them up in a small cup or bowl, and gently immerse the cup in the nursery tank to release the fry (Giwojna, Jan. 1997). Or a common turkey baster works well for gently sucking up one or two of the fry at a time along with a little water, and then releasing them into their nursery (Giwojna, Jan. 1997).

Best of luck raising your Sunburst fry in the refugium, sir! Here’s hoping a few of them managed to thrive.

Happy Trails!
Pete Giwojna

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