Originally Posted by Gregcoyote
I would scrub them in SW
to prevent further die off.
Greg is exactly right. You want to preserve all of the organisms that make your live rock "live". Sponges are almost always dying on live rock before they ever make to the store. Rock is shipped in boxes wrapped in wet paper. Lots of animals survive but few sponges can take being out of water for any amount of time. It's very normal for them to turn black. You just don't want to let them pollute the water that the other little hitchhikers are living in. Scrubbing and rinsing new live rock in saltwater is always a good idea.