I setup my tank in Januaray and I added Miracle mud to my refugium. I have the CPR Aquafuge refugium the biggest one they carry. I added a 5lb jar of miracle mud, my tank had been doing amazing, never had a nitrate problem due to the Cheato growing like crazy, I run a small PC light opposite to my lights in my DT.
From my understanding you dont have to remove ALL the mud, b/c is can crash ur system, but you should replace about 10-15% of the mud every 8months to a year. (about 2 to 3 hand-fulls, depending how much mud you run)
I only bought a 5lb jar, but I regret it, I should of added 10lbs so I can get at least a 3" bed, right now I have about an inch and a half.
All my corals open like i've never seen before, its like some of the tentacles look retarded @ times of how fat and thick they look, especially on my Alveopora.
Only con I can honestly say is the price, but other than that i'd recommend it.
Good Luck