[rayjay]

I'd suggest not putting any other livestock in with the seahorses until you are sure they are not going to have any problems with your set-up and protocol.
If you lose them, you won't know if it was due to a problem with the seahorses themselves, or due to exposure to pathogens introduced by other livestock which is often a problem with seahorses.
I wonder if LiveAquaria keeps the seahorses in separated systems from other fish? If not, they may already have been exposed to a pathogen that will give them trouble once you have them.
Personally I would prefer to buy direct from a seahorse breeder like seahorsesource.com rather than take a chance.