Welcome to the community and the hobby! Seahorses, so fun! I kept a 60 gal hexagon tank with just Seahorses, it was a lot of fun. What temperature are you keeping your water at? I assume you have done some research on keeping them? I'm glad to hear you just calling it a seahorse tank meaning you probably won't be putting other inhabitants in it that will end up competing for the food. Seahorses are very slow eaters that like cooler temperatures and low current. This will be a great opportunity though for some really nice specimens like Carnation corals, gorgonians, sponges, tunicates and x-mas tree worms. You may want to if you haven't already get a nice solid population of Copepods going in there. It will definitely help in the long run; free food for all of your filter feeding inhabitants!
can't wait to see pics of your stable... 
