What I have found is that if you have at least one seahorse trained to eat frozen mysis, it will train the others. I bought one on Monday morning, by the afternoon my veteran male had taught the little female to eat mysis. He taught 3 of them so far, so I'm hoping that the ones I have will teach any new ones. (If not, I'm willing to raise live brine shrimp & mysis shrimp like I used to before.) I read postings from some petshops in the States that related how they've had the same experience. That as long as they keep some trained seahorses that are already feeding, those will show the new arrivals how to eat.
Before my male learned to eat frozen, I had gone through some in the past that I had to raise brine shrimp & keep my tank loaded with live pods & mysis. They also require way too much TLC for most keepers. Even mine still require me to use a turkey baster to target feed them 2-3 times a day. If you're not willing to put in that kind of effort, skip seahorses & keep lower maintenance species. As a tutor, I spend large parts of my day at home so my lifestyle/career choice fits in with feeding & raising seahorses. Most don't.
My dream is to start a captive breeding program & produce Canadian-born seahorses.
Some dream of winning a lottery, others dream of owning their own home, I dream of winning a lottery to buy a home that will house a whole collection of seahorse ranches
If you're gonna dream, dream BIG!!!