Read everything you ever wanted to know about caring for dwarf seahorses at
http://www.seahorse.org
You have to be careful about live rock and sand - could introduce hydroids which pack a deadly sting for the dwarfts. Keeping good water parameters in a 1 gallon might also be difficult, most people go with a 2.5-5 gallon.
Azoo palm filter is highly recommended for small seahorse tanks.
Brine shrimp are pretty easy - do a search on the above mentioned link and you'll find out more than you ever wanted to know!
I am presently cycling a 5 gallon for dwarfs. I can hardly wait!
Carolyn