JasonS,
Are you saying to run the two bottom drains directly into one Vortex and one NEXUSType filter? I was told that this was a timebomb waiting to go off. Thats why I incorporated having a vortex for each of the bottom drains. I'm actually following Maurices set-up...checkout
http://www.koi-uk.co.uk/koi_club.htm . Thats why I have the second vortex with Kaldness media also separate on each line. Maurice mentioned that he has left his system maintenance free for almost a month with no negative impacts to pond or fish. I thought that was right up my alley...of course if I'm home, I'll definitely flush system everyday. I'll be interested in hearing from the other members who are also following his lead to better water quality and significantly less energy used.