Becky--
Do you have the tubastrea in your seahorse tank? The reason I ask is that if you are feeding really high food densities to feed the 'horses, then the polyp is also probably getting tons of food, too.
I used to target-feed every polyp on mine, but that got old very fast. Then I made up one of those feeding hats you see around. Then I realized that I really do feed my tank a ton of food and the polyps have been doing well without any special attention, just catching stray food out of the current. I do have them at a place in the tank where there is a confluence of current from four different sources, so there's tons of flow over the polyps and floating food eventually flows around the polyps.
I've had less growth since I stopped making a fuss over them, but I'm still getting growth (and, apparently, reproduction). So, I'd say if you want maximal growth I would keep target feeding like you're doing. I'd feed it every day if your schedule allows until it stops taking food or your water quality sinks off the deep end. (
) Oh, you do soak your mysis in vitamins, I presume.
BTW, congratulations on getting your mandarin weaned off live food! Mine's very fat, too, but I have to add live copepods to do it.