The way I understand MB7 is it does not introduce any bacteria, it just provides enzymes and "food" (carbon I assume) to help stimulate the growth of bacteria.
I use MB7 every week, as part of my coral snow flocculent treatment. I mix it with some calcium carbonate, rodi water, Selcon, and ZEOFood plus.
I mix about 1/4 cup calcium carbonate with 450ml RODI. This is my CC/RODI mix.
For my 360g volume system I add about 100ml CC/RODI mixture with 50ml MB7, about 15ml Selcon, and about 10ml ZEOFood. shake it/mix it every minute or so for about 10 minutes, then I add it to my system with pumps turned off for 30 minutes. It will cloud the water milky, but settles pretty fast and really polishes the water. After 30 minutes turn your pumps back on. since MB7 binds itself to small particles it is a perfect medium to bind the selcon and zeofood to the calcium carbonate which coats everything in your tank as it settles, directly feeding all your corals and coating your rock and tank walls as well.
If your treating an outbreak with MB7, blast your rocks etc with a turkey baster first to dislodge the unwanted algae before you add the snow treatment.
I got this recipe and treatment from these forums, so I can't take credit for coming up with this, but I have been using it for about 8 months now. Picture is from today.
