Cloudy water during plumbing test?

[lastlight]

Just wondering what the deal is with this? In the tank I have 2 pieces of dry rock. It's live rock I bought a months ago and just boiled in a pot and left to dry for a few months. Lots of flow in the tank while I test things out. Tap water starts out crystal clear and over the course of a few days becomes cloudier. After a week you almost can't see through it down the 6-foot view.

Any ideas?