So I've read on liveaquaria that when you get your live rock, to soak it in a bucket of saltwater with a specific gravity of 1.035 to 1.040 and pests will quickly evacuate the rock. And then you can sort through them and choose the ones that you do want in your aquarium, and discard the others. But, being a newbie, I have no idea which ones are good to have and which aren't. Can anyone offer any help? Mantis shrimp, bristle worms, crabs...who is good and who isn't? Thanks guys!