Hey Ya,
I used to have sea horses and had to constantly hatch them as food. I then thought I'd try and grow them up. I used normal bakers yeast from supermarket (was the dried powder type). Just had an airstone going all the time in a warmish fish room. They grew and did the whole life cycle for months if I was on to it. They are actually pretty cool to watch going about there stuff when they become adults (if you don't get out much like me that is). But you have to be super carefull not to over do the feeding and foul water. I Changed maybe 10% of the water about weekly at best, hardest part is not sucking up too many of the beasts (I usually had a pipe and got a suction going trying to pick up as much gunk off bottom (normally with heaps of eggs but not to stressed on that) I held a fine net on the other end to catch the biggest shrimps (sea monkeys) to feed out. I used the sea water from my sea horse tank for changes, it was the bagged salt mix stuff. they are pretty forgiving.
By the way I used this little round maze device to hatch the eggs. There is a lid on top with a hole in the center. You put the eggs on the edge in water, when the shrimp hatch they swim through the maze to the center hole and you lift up a little sieve - no egg shells, really good to get if you are doing it alot.