I turned off the skimmer for 4 hours when doing the intital 2 week dose, but I don't anymore when I'm doing daily maintenance doses.
FWIW, MB7 really accelerated some colors in my SPS, deepening some greens and bringing out some blue that I didn't even have before. I'm going to continue using and promoting MB7, as its made a nice difference in my tank.
As vice president of LMAS, I'm hosting the first meeting in 2011, and the topic will be about additives in the reef. MB7 will definitely be part of that discussion.