Re:pregnant sunburst on its way

Pete Giwojna

Dear saltfreak:

Congratulations on your new Mustangs! A gravid male is a very nice bonus, but you’ll want to start preparing a suitable nursery for the newborns right away because there’s no way of telling for sure how soon your pregnant male will be giving birth after the new seahorses arrive.

It’s very difficult to judge how far along a pregnancy may be simply from the outward appearance and behavior of the male. He will give some clear indications when he is experiencing labor pains and birth is imminent, but other than that there won’t be much warning. If all goes well, he could give birth a day or two after he arrives or not for another week or two.

However, I can tell you that when you order pregnant males, they are generally in the early stages of pregnancy when they are shipped. That’s because long-distance shipping is too stressful for males that are approaching their delivery date. Unless you actually witness the egg transfer, it takes a week or so for a male who’s carrying a large brood to become noticeably pregnant. So I’d venture to say that most gravid males are shipped out when they are about a week into their pregnancy.

In other words, your male Sunburst (Hippocampus erectus) will probably be perhaps 7-10 days pregnant. Gestation times for H. erectus can be anywhere from 14-30 days days, dependent on water temperature and a number of other factors, but an average gestation of around 2-3 weeks at around 75°F is fairly typical. In short, your pregnant male could give birth anytime within one day to two weeks or so after he arrives. There’s no way of telling for sure.

Your five-gallon refugium would probably make a decent nursery tank if you could keep it from being overgrown with hydroids, which are bound to make an appearance once you start feeding the newborns with newly-hatched brine shrimp on a daily basis. In general, however, a bare bottom nursery tank is easier to keep clean and sanitary. It’s never a bad idea to divide up a large brood between two or more nursery tanks, so if your Sunburst produces a lot of babies, you may want to split the newborns between your refugium and a bare bottom nursery tank and experiment to see which produces the best results for you.

All seahorse babies are challenging to raise and your Sunbursts (H. erectus) are no exception, sir. How difficult or challenging they may be depends on the type of seahorses you have. Two main factors determine how easy or hard seahorse fry are to raise: (1) their size at birth and (2) whether or not they undergo a prolonged pelagic phase. The bigger and better developed the newborns are, the easier they are to raise. Seahorse fry whose average length at birth is 10 mm (0.4 inches) or more are able to take enriched Artemia as their first foods and are relatively easy to rear. Seahorse fry that are significantly smaller than 10 mm (0.4 inches) at birth need to be started on smaller foods that are more difficult to provide in copious amounts on a daily basis, such as rotifers, copepods, and larval Mysis, making them more difficult to raise. Likewise, seahorse fry that undergo an extended pelagic phase, during which they drift freely with the plankton, are much more troublesome to raise than benthic seahorse fry, which orient to the substrate and seek out hitching posts straightaway. The pelagic fry are difficult because the surface huggers tend to gulp air and suffer fatal buoyancy problems, and may even become entrapped by surface tension. As a result, most hobbyists find that mortality is very high during the pelagic phase.

The easiest seahorse fry to rear are therefore benthic fry that are large and well developed at birth. Dwarf seahorses or Pixies (Hippocampus zosterae) fall into this category, and indeed many hobbyists have closed the life cycle with zosterae. The most difficult seahorse fry to raise are relatively small and underdeveloped at birth, and must pass through a lengthy pelagic stage. Brazilian seahorse fry (Hippocampus reidi) are a good example of this category, and are notoriously difficult to raise.

Ocean Riders span the gamut in that regard, including both those species that are the easiest of all to raise and those that are the most difficult to rear, and everything in between. At the one extreme, there are Mo’Olios, which produce very large broods of tiny fry that are barely 3-4 mm at birth and remain pelagic all their lives, even as adults. Mo’Olios are very challenging for even expert aquaculturists with state-of-the-art facilities to raise. Brazileros and Gigantes likewise have enormous broods of relatively small (6-7 mm) fry that undergo a rather protracted pelagic phase lasting weeks. The average hobbyist would still be hard-pressed to regularly raise any of their fry.

At the other extreme, there are Pixies, which produce small broods of large, well-developed benthic fry that hitch from day one. Pixies are probably the easiest seahorses to rear, and no doubt more hobbyists have closed the life cycle with this species than all other seahorses combined. Most of the remaining Ocean Rider types (Mustangs, Sunbursts, Pintos, Fire Reds) produce fry that are fairly good sized (about 8-10 mm) and whose pelagic phase is fairly short (several days rather than weeks), and which are therefore intermediate in difficulty.

In short, saltfreak, your Sunbursts will produce fry that are moderately difficult to raise. They will go through a brief pelagic phrase but will be able to eat newly-hatched brine shrimp as their first food. The link below will take you to an article that discusses how to rear seahorses in greater detail. It will explain how to set up a basic nursery tank and culture the live foods you need to feed the newborns (your Sunbursts are suitable for the "easy" rearing method described in the article):

Click here: – Seahorse, Sea Life, Marine Life, Aquafarm Sales, Feeds and Accessories – Nutrition – Feeding & Rearing the Fry

Aside from the very basic nursery setup described in the article, many other ingenious nursery tank designs have been tried to improve the survivorship of pelagic seahorse fry like Sunburst babies. If you search this forum for "kriesel" or "pseudokreisels nurseries," you’ll find a great deal of information explaining how to set up a more sophisticated nursery for your Sunbursts that may help improve their survivorship. There is a rectangular window in the upper right-hand corner (just above the page numbers) on the forum with the words "search forum" in it. Just type the word or phrase you are looking for into that window and press "Enter" on your keyboard, and the results of your search will pop up in just a few moments.

Likewise, if you search for the phrase "fry feeding schedule" you’ll find tons of information regarding appropriate feeding regimens for hippocampus erectus fry that should be helpful in your preparations.

As for bristleworms, in my experience, there are three circumstances during which these prickly pests become problematic in the aquarium — when they become too large, when they become too numerous, and when they are the notorious fireworms rather than the ordinary, run-of-the-mill, garden-variety bristleworms. Errant bristleworms have powerful jaws and specimens larger than two or three inches in length can deliver a painful bite. (Some species even have poisonous bites, although they’re not normally dangerous to humans; the bite is only about as bad as a bee sting.) Here is what I normally advise hobbyists regarding bristleworms, saltfreak:

Bristleworms In the Seahorse Tank

In general, bristleworms are benign, even beneficial inhabitants of a seahorse tank that perform a useful service as scavengers. But when their numbers get out of control or they grow too large, there comes a point when an overabundance of bristleworms becomes problematic as far as seahorses are concerned. That point is generally when the exploding population of bristleworms become too large and aggressive at feeding time, actively seeking out the frozen Mysis even during daylight hours, no longer content with cleaning up leftovers, and begin invading the feeding station. Too many bristleworms lingering too long at the feeding station brings them in direct contact with the hungry seahorses who come to the lunch counter for their favorite food as usual. The galloping gourmets may accidentally brush up against the encroaching bristleworms, or even attempt to perch on them, and they may get a snootful of bristles when snicking at the same mysid a bristleworm has taken an interest in. Even if the seahorses don’t inadvertently snick at them, the bristleworms may shed a few of their irritating spicules while they are at the feeding station, and the hungry seahorses can then accidentally ingest such loose spicules when slurping up frozen Mysis. Captive bred seahorses are aggressive eaters that are accustomed to slurping up food from the bottom, and it seems at times this may also lead them to strike at baby bristleworms. I’ve also heard a few reports of seahorses that snicked up a tiny bristleworm and got them lodged in their snout or throat. It’s unclear in these cases whether the bristleworm was accidentally sucked up while the seahorse was targeting a piece of nearby Mysis or whether the seahorse actually mistook the tiny worm for something edible and deliberately struck at it, but this is another potential danger the seahorse keeper should be aware of.

I have seen pictures of seahorses with bristleworm spicules embedded in their tails and snouts as a result of such close encounters. These injuries are usually minor, easily treated by removing the spicules and administering antibiotics orally via gut-loaded shrimp to prevent secondary infections, but the more bristleworms there are, the more likely such incidents and problems are to occur.

I have seen a few seahorse tanks that were overrun by them to the extent that the bulk of the total biomass in the aquarium consisted of bristleworms! When that happens, they are detrimental simply because of their effect on the water quality. Under certain circumstances, the total metabolic activity of the countless bristleworms may have a greater impact on the nitrogen cycle that all of the seahorses and their tankmates.
So when you start to see bristleworms swarming the food station, or spot big bruisers longer than a couple of inches, it is a good idea to start thinning them out. Most seahorse keepers find that a combination of trapping large bristleworms and using biological control to reduce the the numbers of small bristleworms works very well. Let me know if you would like to discuss some methods for controlling bristleworms in greater detail, and I won’t be happy to elaborate. A number of bristleworms traps are available at aquarium outlets and can serve as the seahorse keeper’s first line of defense against these prickly pests.

Best of luck with your new Sunbursts and their offspring, saltfreak!

Happy Trails!
Pete Giwojna

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