Before buying seahorses, do a ton of research on them. Captive bred are much easier to feed than wild caught. WC will require live foods until you are able to train them to eat frozen, if they ever do eat frozen. Make sure your tank is well established with macroalgae for the seahorses to hitch onto. A feeding station is recommended. Low flow and low lights are also recommended, as well as is making it a species tank.
Two sites on seahorses:
http://www.syngnathid.org/
http://www.seahorse.org/