Funny how this discussion slid off timed flow to towers....hehe. Nutrients seem to be far more interesting. On that topic I have been mulling a question for Rupert: With your knowledge of AP systems and crops, you have recommended a hydroponic literature source to me in this thread. In the older stuff I have (Savidov, UVI) there were often statements made to the effect that "AP does not operate like hydroponics" and that the nutrient availability and use patterns are completely different. Is this being contradicted by the Aussie experience with media bed systems? Can one safely assume that meeting a plants needs described in hydroponics would be exactly the same in aquaponics?