I have quite a bit with it. I have used the Fiji mud and miracle mud. I personally like the Fiji stuff better because I think it lasts longer and it comes wet rather than dry. I have noticed improvements in coloration and general happiness of corals since I started using it a few years back.
Julian Sprung indicates that it's helpful, needs to be changed out in phases, about a quarter per year. I haven't used it, just repeating his comments.
I use it on a large seahorse system and It works great also has mangrooves. Personally its not really a fuge but I firmly believe it helps. Just change 1/4-1/2 every year and it works well.
It would not add nitrates to your system if you added it. I've been using the ecosystem for over 5 years with great success. I've used mud only systems and skimmer/mud systems. Both work great. I've never had nitrates with an ecosystem no matter the bioload. You still need to run GFO or PO4x4. The most important factors is surface area of mud and flow over the mud. Give Leng a call. He is very helpful and willing to help anyone. If you have any questions on footprint of fuge and flow just let me know.