It looks like you turned your tank into a curing vat
Ive seen shipments of live rock turn vats black, so I wouldnt worry. You just have some more work to do before getting your tank up and running. Things could be worse. If you dont have a skimmer yet, my advice would be to keep changing water. Treat the tank like its a curing vat and change as much water out of there as you can until it pseudo clears up. Adding an airstone will help as well to get more O2 into the system. I would definitely be looking for a skimmer.