Hi Joe:
I have - in my own tanks, and did in my ATS system (but that was prior to adding phytoplankton) - and I always find very few cells. Surprisingly few, actually. A person to ask would be Morgan Lidster (inlandaquatics.com) - he has the tanks, and he has the lab and I'm sure knows the answer.
EG is apparently Environmental Gradient - I believe it is a term from Steve Tyree's book, if I can extrapolate from the post well enough.
