I thought they would be filtered out too, but I am told that they do not get filtered out - they just stay in suspension. But I have had my water tested after the treatments and they test as no metals, so I don't really know. I do know that if I keep my water treated with the sequestering agent I don't get the stains back. I keep reading all I can about the metals in swimming pools, but there doesn't seem to be a way to filter the metals out, except by doing it a way that Pool Doc says - but it involves careful control of ph and bleach to get the metals to fall out on the filter. I don't have a complete understanding of it yet. If anyone out there can chime in and give a better answer, please do!