Thanks for all the replies. After one more vacuuming I put my Polaris back in and it keeps things stirred up enough that I haven't seen too much brown stuff. It's still too cold to check out the feel of the bottom. I don't think my old Hayward filter has been serviced in a long time so I may tear it down and change the sand and check out the laterals. This is my third summer in this house and I have never seen this before. I love this forum though. It is a real blessing to all of us relative newbies.