Only Chinese imported blood clams are (because of poor sanitation controls leading to things like Hepatitis infections in people from the blood of the clams). Blood clams from other places are considered fine (I wouldn't recommend eating any blood clams you're adding to a tank though).Aren't blood clams illegal?
I have no idea if it'd be possible (mostly because of how destructive these guys are so couldn't imagine a reef) but a tide pool mangrove style tank with halloween moon crabs (Gecarcinus quadratus) sounds fun to try since they need both land and saltwater.