Well I agree with Bill B., could be wrong, but I do. This rock is supposedly already dead, but either way you are placing it into a new setup so in theory it should just help your tank cycle. Maybe I sinned, but I added about 50% dead rock into my current setup well after the tank was cycled, and I never saw any kind of cycle nor did I have any "bad" hitchhikers. Maybe I just got lucky, but thought I would share.