Another thought on the topic of flow and why some things work for 1 person and not for another is that the SPS in Micki's tank have prob become acclimated to the amount of flow she has, which would explain why she got less PE when she made a change. If she added more random flow and observed for a period of months, she might see more PE instead of less. Bsinger, your situation might be the same... you take away flow, and the impact appears to be negative. I'm not sure if the initial negative change would be permanent or not.
Just a thought...