Join Date: Mar 2011
Location: Oregon State Beavers!
The whole point of this system is to not let your plants ever run "dry" of any particular nutrient. You could try and determine the exact uptake levels of your systems and then determine the exact dosing that is required to meet that, but there is multiple problems with that like regularly inaccurate testing results, measurement errors, changes in tank uptake, etc.
When you dose EI you always have enough nutrients to satisfy your tanks requirements, but never so much that you reach toxic levels. Obviously you don't want 200 ppm nitrates in your system and reducing everything by 50 percent each week prevents this from ever happening. Read Tom's article about it on his website the Barr Report. Yes you are "wasting" nutrients each week, but they are dirt cheap compared to testing equipment, and personally, my time.