People think that the other stuff that comes with the LR is what makes it live, Well the other things, the algae, the crabs, snails, sea urchins, starfish... the list goes on are just "Hitch hikers". It is the bacteria let Mike stated that is the only factor to making the rock live. Now having the choice between a plain rock that someone says is live and a rock that looks full of hitch hikers I would pick the one with the hitch hikers any day. IMO