Honestly, I don't know much about seahorses, but over at that bulletin board the prevailing thought is OH MY GOD HYDROIDS ARE EVERYWHERE...AND THEY WILL KILL YOU IN YOUR SLEEP...
Sheesh, how many of us really have hydroids in our tanks? The overwhelming opinion over there is also not to use any live and or live rock in their tiny little seahorse tanks that they pack with tons of brine shrimp. It's pretty sad.
Sorry, end of rant. I just really think that site has some screwed up people handing out advice.
~ Sherri