The only seahorses suitable for a 10 gallon would be the dwarf variety. Pipefish would not do well in a tank that size. Seahorses need tall tanks, the general rule of thumb is 3 times the adult length in tank height. Also, there are other fish that do ok with seahorses. such as scooter blennies...anything that is not a voracious and fast eater, or hyperactive will do ok. The other challenge is filtration without alot of current. seahorses tend to get blown all over with heavy current. I use the tetra tec filter on my seahorse tank and it does well. When buying seahorses, try to make sure they are captive bred. Bare minimum, ask to see them eat while you are at the store. frozen food, not live, or you may well end up with horses that wont eat at all and slowly starve.
Along with the source that reefrunner gave you, there is www.syngnathid.org
I would also caution you that seahorses are not for the beginning saltwater enthusiast as they are very demanding about water quality and stability issues.