I used to breed seahorses (H. hipocampus and H. guttulatus) somes 20 years ago.
I would recommend minimal flow (really minimal), very stable water parameters and lots of macro algae (you mar use caulerpa taxifolia - very strong and easy to propagate). You can get it already grown as long as you transport it in damped paper, it´ll hold.
You may algo use dead gorgonians (skeletons) for decoration that will be used by the seahorses
The complicated part would be to have frequent water changes without messing with the water parameters. So, change the water very slowly, using an air pipe to introduce the new water.
Which species are you considering? Another advantage of having lots of macroalgae is to create a refuge for propagation of small crustaceans (artemia and rotifers) thus providing a constant source of live food for the dwarfs.
Keep us posted