Don't I want those creatures, and how do I tell
what I want to keep and what I want to get
You'll need to familiarize yourself with pics of mantis shrimp and any hitchiker crab is no good IMO
. You want to keep things like copepods, amphipods bristle worms peanut worms spaghettie worms etc.
to either do a high or low salinity dunk to get rid of
creatures on the live rock.
One of the better methods I've read about is to make some SW
at the same SG
as your tank, but instead of using RO
to make it, use carbonated water. The fizzing from the carbonation drives the critters batty and they flee the rock trying to get away from it. You'll need to be ready to scoop the wanted critters back into a bucket of regular SW
, but it should help tremendously. Hyper or hypo saline dips are very unreliable.