Just my opinion, and it ain't worth much, added chaeto for filtration is good, adding it for adding pods , and other critters is good, if you want a steril tank, well eventully mother nature will win out, a fish a rock or algea will eventually add something to the tank. You can fight it, or embrace it as a wouderful thing, part of the beauty of salt water is all of the life forms that evolve and eventually find there way into our tanks. Some good some not so. Some come in like a plague, then seem to just dissappear on there on. If you are going to have certian fish, the pod population will be greatly improved with the chateo. I wouldn't worry with the white calcium like formations, looks like the small tube worms that form in time in the bottom of the sumps . If you are concerened just keep it quartined. Wash it in some freash clorinated water and rinse it out in a bucket several times, that should kill off any unwanted critters. Hope this helps. Looks like you have a good set up going.