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Congratulations on your 2-1/2 week-old fry! You’re doing wonderfully well for your first attempt at rearing!
Things will start getting a bit easier and less time-consuming once the fry are weaned off of newly-hatched brine shrimp (Artemia nauplii) onto frozen foods (e.g., minced Mysis or Cyclop-Eze), which is something you will be working on shortly, so hang in there. Aquaculturists are now converting the fry to frozen foods earlier than ever, often beginning around 3-4 weeks old. Jeff Mitchell (Senior Aquarist at the Shedd Aquarium) reports that the fry are healthier and grow faster the sooner they make the transition to enriched frozen foods, and he expects the young seahorses to have made the transition to frozen foods by the age of 4-1/2 weeks.
The best way to prepare the Mysis for this is to mince the frozen Mysis coarsely rather than putting it through a blender. How fine or coarse you need to chop it depends on the size of your fry, since you want to wind up with bite-size pieces of Mysis. Initially, many breeders prefer to shave small pieces of Mysis off of a cube while it’s still frozen.
When the fry have grown a little larger and can accommodate bigger pieces of Mysis, I find it convenient to carefully thaw whole Mysis individually and then carefully chop them into several pieces.
Either way, it is very important to be extra diligent about vacuuming up leftovers (and any fecal pellets) while the fry are making the transition to frozen Mysis. Otherwise, the minced Mysis that doesn’t get eaten right away while it’s still suspended in the water column or shortly after it has settled on the bottom will begin to degrade the water quality in your nursery tank.
It’s important to overlap the fry food when they are making the transition. Offer them shaved or minced Mysis along with the newly hatched brine shrimp they are accustomed to eating. (Many times it’s better to offer the minced Mysis first, while the fry is still the hungriest, and then add the baby brine shrimp.) Once they begin eating the bits of frozen Mysis well, gradually increase the amount of minced Mysis and decreased the amount of baby brine shrimp you offer at every feeding until they are finally eating the shaved Mysis almost entirely.
Overlapping the feedings this way, offering newly-hatched brine shrimp as usual along with just a little frozen Mysis at first, assures that there is familiar food available to the fry while they are making the transition and makes sure that the slow learners still get enough to eat.
Some hobbyists find it helpful to begin soaking the newly hatched brine shrimp in Mysis juice for a week or two before they actually began offering the bits of minced Mysis along with the bbs. That way, the juveniles get used to the scent of the frozen Mysis and associate it with food before you start to add the bits of frozen Mysis.
Here’s a previous post from Patti from the Ocean Rider Club that describes how she weaned her erectus fry onto frozen Hikari Mysis:
I’m wondering if nutrition is your problem.
Could you train them onto frozen mysis? My 4 week old erectus are
eating shaved Hikari frozen mysis already. They started not eating
much of the BBS and looking around the bottom of the bowl. I
enriched the shaved mysis w/Vibrance & put it in the bowl. It goes
to the bottom and they’re on the hunt. They’ll look at it a good
while and then snick. It only took 1 day to train them. I swish it
around a little at first to get them interested.
I think the mysis is better for them nutritionally and they don’t
have to spend so much energy eating all those tiny BBS. Give it a
try. It may take a few days. I gave mine the mysis 1st – before
adding the BBS. That way they were pretty hungry. Then I gave them
some BBS for desert to make sure each one got something to eat if
they weren’t eating enough mysis yet.
Patti [close quote]
Notice that Patti’s erectus fry were all hitching and beginning to look around on the bottom for things to eat, indicating that they were ready to give up their planktonic existence (the high-risk pelagic phase) and make the transition from live brine shrimp suspended in the water column to frozen foods.
When the newborns are the right age, don’t hesitate to try them on frozen Cyclop-Eze first if you aren’t having any luck with the frozen Mysis.
Your 10-gallon aquarium will serve nicely as a grow-out tank for your fry for the time being, Barbara. It’s perfectly acceptable to mix cohorts when rearing, so you can add your male’s next brood to the same 10-gallon tank right alongside the older juveniles. The suggested stocking density for seahorse fry is no more than 80 fry per gallon (20 fry per liter), so your 10-gallon aquarium can house up to 800 fry up to the age of two months old. But of course the more crowded the nursery is, the more diligent you must be about making water changes and maintaining optimal water quality.
The best way to keep your fry population at a manageable number is by culling the newborns, as described below, Barbara:
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).
Bear in mind that if you do not cull out the weaklings, Mother Nature will be happy to do it for you. The disadvantaged fry will still be weeded out and die during the rearing process, but they will jeopardize the healthy fry in the interim by consuming your precious resources, polluting the nurseries, and increasing the chances of disease spreading throughout the nursery. Culling will occur, one way or another, and it’s best for the hobbyist to do it immediately rather than to prolong the suffering and put the healthy young at risk while the less fit fry are slowly eliminated nature’s way.
Best of luck with your prolific ponies and their progeny, Barbara!