Come down 95 and cut across 495 over to Jays/Oceans in Glass and Aqua addicts all in Salem NH area. This is not an endorsement of any kind, just trying to help if you are not familiar with the area. You might want to try calling ahead.
I'm with Flame Angel on this one.. I'm close to the border and there isn't anything worth going to. there's a fish store in seabrook, NH but its more freshwater. i wouldn't recommend it for anything marine...