Dainichi Goldfish COLOR MAX 250g Small Sinking Pellet
Now, all Dainichi goldfish formulas contain calcium montmorillonite clay. This bentonite clay contains more than 60 mineral compoundsand has been proven to be immensely helpful in enhancing digestion and growth, as well as neutralizing metabolic toxins...a function especially important in a goldfish aquarium. In an artificial environment such as a fish tank, the clay helps return minerals to the water and stabilizes its chemical make-up.
https://www.youtube.com/watch?v=wWSiOQYa_tc