Brown Powdery Sediment in Bottom of Pool

I battled this all year last year and its back again! It is a fine brown/tan sediment that vacuums very easily or just disappears if you brush it or walk through it. I have vacuumed in the evening, closed the automatic cover, opened it the next morning and it's back. I vacuumed to waste several times last year but it would show up again every few days. I'm absolutely positive it is not sand. I sucked it up with a turkey baster one day last year to take to the pool store (they were clueless) and it just dissolves then after a few hours settles back to the bottom. Please Please Help! I am at my wits end. Ready to fill the pool in with dirt and make a garden:-) I have pictures if there is a way to post them. Thank you for any help.
Lisa

27,000 gallon IG concrete pool installed in 2000, owned by me since 2009.

Are you sure it isn't just dirt? I know after I vacuum and the water settles back down, I always find a little dirt on the floor. While you are vacuuming, the dust/dirt gets into suspension and you don't see it but then once the water quiets back down, it then resettles on the floor. Do you think this might be what is happening in your pool?

Welcome to the Pool Forum, by the way!