New Sand

Hi everyone. This is actually an update with some questions. After getting help here it was determined that my sand was phosphate loaded beyond help. Last weekend I changed out a 24" section of sand. My tank is 72" long. I used the Caribsea Seaflor Special Blend. (Dry sand) Here are my questions. Because it is dry sand, I am putting my rock on it to help it become live. If my rock has cyno on them which some do, will that get into the new sand and give me the same problem of brown stuff again? Question 2. When I would mix up my old sand to get rid of the brown, it would be back very quickly. I was happy to see my new sand not doing that but last night I noticed a very slight discoloration in the sand making me nervous. Will the sand do this like a new tank does? I know a new tank will cycle and sand will get brown etc... Will just a section of new sand take on the same properties of a new tank?

Thanks for all your help. I will keep you posted as next week I will probably do the next section of sand.

David