Yes, indeed, seahorse fry typically require suitable live prey in order to achieve acceptable survivorship rates. Newborn seahorses will also be rotifers, larval copepods and early larval Mysis, among other living prey, in addition to newly-hatched brine shrimp. However, it is much more difficult and much more expensive to provide these alternative live foods in the quantities necessary to raise seahorse fry, Artemia nauplii (newly-hatched brine shrimp) are the most practical live food for the home hobbyist to provide.
Some breeders report limited success rearing seahorse fry on nonliving foods such as freeze-dried or frozen Cyclop-Eze or preserved zooplankton, but the vast majority of newborns will not except such offerings, at least initially, and losses are typically very, very high for those who have tried such shortcuts. The non-living food simply doesn’t move right, and usually fails to elicit a feeding response from the fry.
Frozen Cyclop-eeze and preserved zooplankton can be great time savers when rearing fry but they do have one other very big drawback. They are not feed-and-forget fry foods like Artemia nauplii or live copepods which survive until eaten and keep swimming around until they pass within striking distance of one of the babies. If the preserved zooplankton isn’t eaten quickly, it will settle out of the water column and begin to degrade the water quality in the nursery. So if you are relying on Cyclop-eeze and preserved zooplankton to make up a large portion of your frys’ diet, you need to be even more diligent about making water changes and siphoning off the bottom of the nurseries in order to stay on top of the water quality. You will certainly need to increase the frequency of the water changes and/or increase the percentage of water you change each time, if you try such foods.
Years ago, I did receive one report from a hobbyist overseas who was successful in raising a brood of Hippocampus barbouri babies to a three-month old juveniles using prepared foods, after which she was able to successfully wean the juveniles onto a staple diet of frozen Mysis.
As I recall, this hobbyist was successful using ZM Fry Food (ZM Fish Food & Fishroom Equipment, a.k.a. Zebrafish Management Ltd., based in the UK) for raising her baby barbs to young adults using only prepared foods.
The ZM Fry Food is semi-buoyant when first added to the aquarium so that it stays suspended in the water column longer and simulates live foods. The ZM Fry Food includes shrimp meal which acts as a odor attracted to help stimulate a strong feeding response, as well as stabilized Vitamin C & Vitamin B-12. And the ZM Fry Food is that it’s available in a number of different particle sizes, which are suitable for fry at different stages of development.
For example, the ZM-000 Fry Food has particles that are less than 90 microns in diameter and can be used as an alternative or supplement to live rotifers for fry that are too small to accept newly brine shrimp, such as H. reidi fry.
Likewise, the ZM-100 Fry Food has particles from 80-200 microns, making them a little smaller than most newly hatched brine shrimp. That would make them a possible alternative or supplement for newly hatched brine shrimp (1st instar Artemia nauplii).
The ZM-200 Fry Food (150-200 microns) is similar in size to newly hatched brine shrimp, and can be used as a substitute for Artemia for fry that are a little larger and ready to accept 2nd instar brine shrimp.
And the ZM-300 Fry Food (300-500 microns) could be offered to the juveniles when they are ready for slightly larger food, and so on.
If seahorse fry will actually accept the ZM Fry Food, that would be a tremendous boon for seahorse keepers, especially the home breeders. Offering these particle foods to the newborns and young seahorses would be much more economical and convenient, sparing the hobbyist from the hassle of culturing rotifers and copepods or preparing copious amounts of newly hatched brine shrimp on a daily basis.
So if you could possibly obtain some of the ZM Fry Food from the manufacturer in the UK, that is something that you might try for raising seahorse fry on nonliving foods.
Best of luck raising your surprise brood of babies, or at least the remaining survivor(s)!
Happy Trails & Happy Thanksgiving!