The leading koi experts in the world agree that the clay that contains the most minerals and trace elements is bentonite / montmorillonite clay. There is very little, if any, bentonite clay in our yards and gardens. This type of clay has to be mined and processed to a consistency that will allow you to add it to your pond. Even though there are mines in several places around the world, not all bentonite clays contain the same level of minerals. That is why we spent the time and effort researching to find the best source to make sure our clay is high in the needed minerals for your fish. You can be assured that "Ultimate Koi Clay" has been laboratory tested to confirm it will provide the proper minerals for your fish when used according to our dosing instructions. Try it and you will see the difference in your water, your fish and your pond.