I dont think seahorses are terribly 'hard', but they do require a tank set up with the mentality of 'this is a seahorse tank' and being strict about maintaining that.
The biggest things are temperature (no higher than 74), getting good livestock from a true captive bred source (and not mixing sources), and having a reasonable understanding and ability to treat various issues that come up. Rayjay in the seahorse forums has a good basic writeup that he calls his thoughts on raising seahorses, it gives a great idea of the big issues that you will have to overcome. I am more than happy to help as well.
Cheers!
Chad