Miracle Mud became popular for refugium substrate about a decade ago. The claims are it's natural substrate from estuaries that contains supplies of minerals that assist macroalgae and even coral growth such as iron, manganese, stuff found only in lagoons feeding coral reefs.
It all sounded plausible to me until a few people started analyzing the contents and found things like sticks, grass roots, crickets, stuff you would find if you put a shovelful of dirt from your backyard into a fancy bucket.
