Okay instead of doing this all over again try my new forum. Go to the seahorse category and look at the sticky. It's a long article type thingy I wrote on them, not totally finished but it should help out some.
Try going for a 30 gallon tank. That should house a pair of H.reidi just fine. Any smaller than that and your getting into coldwater species like H. Capensis.
Just to clue you in on something, A tank with bare bottom and a filter isnt going to do if you didnt know. sEAhorses arent something to go cheap on. They require a lot more attention than your average clownfish and at 120 dollars for a pair you dont want them to die.
Try oceanrider.com. has some great seahorses for sale and a greal deal on reidi.