"Ultimate Koi Clay" is a high quality calcium bentonite / montmorillonite clay powder that will replace minerals and trace elements that have been leached out of the pond water by the fish and plants. While in suspension in the water it will not only release minerals, but it will also attract and absorb heavy metals and other toxins.
I've used this on a sporadic basis ever since I've had a pond. It always amazes me as to how clear the water turns after a treatment. Glad to see your still with us, Gene!