We closed our above ground pool around a month ago. We use a cover that stretches tight over the pool. It filters water in through a few filter strips in the middle of the pool and we've had a Lot of rain lately so I checked the water level and found blue specks in the water. After browsing online most things I can find state it's copper but this looks like plastic to me. Here are some pics. Our first thought was it was from the cover, but it's only 3 years old and should be lasting at least 10.