you can also add LR later but make sure it is fully cured before placing it with the fish. so far I have been able to purchase only cured rock from my LFS he cures it himself before it is placed into the selling tank.if you purchase LR from online be sure to cure it first.its simple to do. be sure to cycle your tank well before adding any fish.for questions on cycling of a new tank you can also check the comments on new hobbiest for this forum you will find it very informative i think.unlike fresh water fish marine fish aquariums take time to get just right before adding livestock.