live rock

We've bought cured live rock from our LFS frequently. Smell usually doesn't enter it...LR has an odor that I notice, my boyfriend doesn't. You can ask the LFS, and look for dying critters when you pick out your pieces. If it has some decaying organisms, it might raise the all parts of the nitrogen cycle, not just the nitrates.

Yes you can if it is cured. Uncured rock will have a definite unpleasant odor. Can't mistake it. Cured will have one as well, but it's a natural, ocean smell.

ANything you add to the tank which increases the bio load will also eventually increase nitrates. The key is to add slowly so the filtration has some time to catch up and you won't notice any spikes.

HTH

if you have nothing in your tank, you could add either directly...