Sach's Aquaculture
http://www.aquaculturestore.com./swinverts.html is one of the best live food suppliers around. They can Overnight Ship rotifers to you.
Newly Hatched Brineshrimp (nauplii less than 24 hours old and still have their yolk sacs) are highly nutritious. After 24 hrs, BBS need to be fortified with Selcon or other supplements. For that matter, the rotifers themselves offer very little nutrition aside from what you feed them (phytoplankton, liquid invert food, yeast, etc.).
Decapsulating Brine Shrimp Eggs give a better hatch rate(also hatch much faster) and you are less likely to introduce hydroids to your seahorse tank.
http://sfbb.com/faqs.asp#