Yes that’s exactly what I was just doing for the past hour pulled out a couple pencil urchins and a couple starfish and then decided to move about 30 to 40 pounds of the 200 is my system that runs through a filter sock hoping that it should catch anything that tries escaping the tank and going throughout the rest of my system. And as far as the tapwater I do drink the water without being filtered Chicago has some of the best water I’ve heard but it does have chlorine in itYou have an established system, right? Why not start pulling any macro hitchhikers (starfish, etc) that you want to keep and putting them in there instead?
The main benefit of ocean live rock is all the bacterial diversity. That's not going anywhere, that stuff's tough.
And, how bad the tap water would be depends on your tap. Some people have copper in their tap water, for one thing. Some people have tap water that isn't even safe to drink. Some have water that works fine for a reef, particularly if you don't mind algae. Most people have water somewhere in the middle.