I have noticed in many threads calling for the use of montmorillonite clay (aka bentonite, koi clay). The calcium varies based upon source from 4 ppm to 23.7 ppm per teaspoon per gallon of water. There are other elements such as iron, magnesium and silica. For use with koi it helps clarify water and supposedly enhances color. Like golfers who would buy anything to reduce a stroke from their game koi enthusiasts would buy anything to enhance color. With all that said is this clay useful or a gimmick for shrimp? For openness I use the clay in my koi pond.