ccCapt, new frag disks/plugs will raise your ph level and need to be cured before putting straight into a established system. They come pre-cured so it shouldn't be a problem. This is the only reason I can think of!
because it made out of the same stuff as most of the sand we buy is, its safe but unless your a farmer i dont think it would be a problem to not be able to put 20+ frags in your tank.