I learned a long time ago to buy LR
from my local LFS
, and from tanks where there are live fish swimming around. This way I'm insured it's nearly fully cured and don't have to put up with these hassles. It may not be nearly as cheap as Crazy-Achmed.com's '$2 a pound' Fiji special, but I also don't have to spend evenings playing with plastic garbage cans and a really big mop.
If you're buying raw (uncured), or partitially uncured LR
you do have to condition it before even thinking of putting it in a production tank. The critters don't scare - ammonia spikes scare me.
Easy enough to put the stuff in a garbage can or other big plastic container for a week or two. I *strongly* recommend keeping the temp between 75F-80, and an even stronger recommendation is to keep strong water circulation in the container via powerhead or spare back filter. No water circulation = no oxygen and thus killing off many beneficial bacteria. Low temp = a slower decomposition process and longer break-in time.
I can't help much with getting rid of possible bad hitchhikers, since the worst I've had is aiptasia, and a fresh water dunking only gives those a buzz. Usually keeping the rock out in the air for awhile while cause bristle worms and other critters to bail out.