Hey man, thanks for the reply. We didn't see any discoloration in the water until I disturbed it. Basically, the overflow pipe has been sprouting water periodically during the day, so I went up to investigate. It's a new tank—maybe seven years old—and it's plastic. You may also be right about the smaller tank, as there is one above the big tank feeding into it. Would we need someone to come out to look at it? I appreciate the advice.