If it's not already cured then yes you will have dieoff and mostlikly another cycle and you chances get better of having a cycle with the more uncured rock you get. If it cure and your getting it from a LFS to your tank then you should be fine, but to be on the safe side keep the rock under water in a bucket to keep die off from happening.
Buy fully cured live rock.It should smell fresh.Like Bobby said even cured rock can have die-off so keep it underwater if you have any worries.If you buy uncure,cycle it in a separate container before adding it to the DT with fish,corals, or inverts.
i agree...if you get uncured at low price..and if the tank is cycled, which is the one your gonna ad the uncured..cured it in a plastic container with a power head and air stone.. making regular water changes, testing the water...ill be cured in alsmost 2 weeks...then you can add it with no probs
When in doubt cure it yourself..... My LFS has 7 huge tanks of live rock and sand always cycling so I dont worry about it..... if they get a new shipment in they label it for a couple weeks.
BTW David I sure enjoyed watching my M's sweep those socks this week!