I had
LS in my tank for a few days before i put my
LR in. Like the above posts said, it won't hurt anything, just put it in when the
LFS gets it and wait (be patient!) untill the tank levels are normal. The rock shjould be cured if the the levels are normal and if it doesn't smell bad(uncured
LR will actually smell bad). The one thing i have learned in this hobby is to never rush anything and to be patient.
HTH!