Its typical use is for sumps becuase of the added iron growth of algea in the sump is increased which is in turn supposed to take out more nutrients from your system.
There have been many reefers over the years that have used it and had nice colorful stony reefs, I believe Sue T from Tx had a ecosystem reef at one point.
I dont and never will use it, as I feel there are better systems out there to use.
miracle mud is a joke, its hardly even organic, who knows what it is , the consistancy of it, noone knows, i say go w/ a nice aragonite DSB in your fuge, else you are buying snake oil.