From what I've read, the problem with a DSB is depth. Too deep and you create a true anoxic zone where the bacteria creates sulferic acid, too shallow and you won't have enough of an anoxic zone to finish the nitrogen cycle. The going estimate is 4-8" in order to be deep enough to complete the cycle but shallow enough to prevent a tank crash if its disturbed. In regards to the miracle mud, outside of what ever extra is added to the mud to make it a "miracle", it works the same as a DSB when it comes down to creating a habitat for the startification of bacteria.