The current thinking is that the fry can remain on a steady diet of newly hatched Artemia until you are ready to begin weaning them onto a diet of frozen foods (usually minced Mysids and/or Cyclop-eeze). Aquaculturists are now converting the fry to frozen foods earlier than ever, often beginning around 3-4 weeks old. Jeff Mitchell 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 that describes how she weaned her erectus fry onto frozen to Kari 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.
Best of luck weaning your fry onto frozen food, Nigel!