I wouldn't trust most LFS' with info on seahorses...
I've read a little on Dwarf Seahorses, and what I've gleaned from my reading is that they require live feeings of BBS (Baby Brine Shrimp) and that the tank they go in has to be practically sterile as far as LR and LS go... If aiptasia/hydroids hitch-hike in, they can kill the 'horses, so that's why some people even opt for a completely artificial enviroment, with the exception of chaeto for pods and other foods, as well as for hitching.
Because they're so tiny, it's not really recommended that anything else is kept with them, although some do "go against the grain" and keep a goby or blenny in the tank.
As with any seahorse, Dwarves require pristine water conditions, especially when kept in a smaller tank. They don't have much of a digestive tract, and their food basically goes from mouth to bum, and therefore the water gets dirty quick.
There are many other things to cover, but the short end of it all is that Dwarf Seahorses are not recommended for beginners.
There are a few people on this board who are knowledgeable, and there's another seahorse forum on the internet as well... some of the people there can be nazi's though, but I think you find that everywhere
Good luck!