Depends on the type of live rock that you bought. Was it "cured" or "uncured"?
Cured live rock will take longer, but it will also be free of bad hitchhikers. Fresh "uncured" should have stuff visible already. Much of it will die, but new will spring up pretty quickly.
Macro algaes may never "spring" up. Fish like to nibble at them before they ever gain a foothold.