I've kept seahorses for years.
They are extremely difficult and require much more time to maintain than regular reef inhabitants. My thoughts off the top of my head:
1. Have a high tank, seahorses like tanks with depth.
2. You need to feed them live food almost every day (mysis with vibrance is the recommended food). My seahorses in the past seemed to like only one type of mysis. They also liked live brine, however, it provides no substance for them.
3. Do not put fish that eat mysis in with seahorses, they will always beat out the seahorses for food.
4. The tank should be a low flow tank, since seahorses can't swim as well as other fish.
5. Huge skimmer to remove excess nutrients from daily feedings.
6. No stinging corals! forget anemones, etc.
The perfect tank would be a macroalgae tank, with gorgonians through out, that is 2 feet high (65 gallon or above), low flow, T5 lights with one MH, and lots of cleanup critters. As for other fish, maybe an algae blenny would be OK.
Right now I don't have any seahorses, and to be quite honest, I am HAPPY! They were the most demanding pet I have ever kept, but beautiful and rewarding nevertheless.