Should be an interesting experiment, one I would not be willing to try with that size tank. I feel that is waaaay to short of a tank for seahorses, they need tall tanks to be happy. Seahorses swim up and down, not side to side like fish. Also, if I ever were to setup a tank like a 75G Hex tank just for seahorses, there is no way I would ever think of putting a fish in that tank, and definately would not put any corals in that tank. I know your excited and not trying to burst your bubble at all, simply stating my opinion.
Heck, I can't get any pipefish to live for more than a month at the LFS I work at and that is in a well established tank suited perfect for them (175G bowfront with super low flow and a Solaris G series 6' LED fixture). After losing over $300 in pipefish over the last few months the owner finally said we had to call it quits on trying to keep them. None of us have ever considered trying a seahorse due to the fragile nature of them, nor have we even bought one because we have never had a request. After we show and explain to people what it takes to make a happy seahorse environment everyone says forget it.