Using Miracle Mud as as a substrate

[tprize]

Well we all know how expensive miracle mud is. A lot of us use it in our refugiums, because of it's great filtering capabilities. So my question is, will this make a great substrate for a small pico or nano tank? Advantages I can think of

1. I never see ugly algae growth on my miracle mud.
2. Great filter system right in your tank.
3. Different look

So let me know what could be some potential problems with the miracle mud as a substrate.