Part of the "beauty of EI" is supposed to be that you don't have to measure. Some like to, some don't. In my understanding of EI and the way I make up my solutions, it is to bring the tank up to a certain level. For example, adding 15ml's of my macro solution increases my tanks nitrate by 1.25 ppm and PO4 by 0.25. If I added them to a tank that was half the volume it would increase the nitrate level in the tank by 2.5 and PO4 by 0.5. The salts used in EI are very concentrated and it doesn't take a large amount to raise tank levels by a significant amount.
I think the accepted level for nitrate in a tank based on EI is 10-20 ppm. That doesn't mean adding 10-20 ppm but having an overall tank level of 10-20. If your water came out of the tap with 5 you would adjust dosing accordingly. But once again, the beauty of EI is that you don't need to measure and you customize it completely for your tank. Just following standard EI amounts and following a 50% weekly water change should keep levels in check, theoretically. Although some will debate that.
Personally, I still consider myself to be using EI although I dose significantly less than what many would consider EI because they don't get the point of EI. It isn't just to dump x amount of ferts into your tank and control them with water changes. It's to find what works for your tank by finding the amount of nutrients needed to keep your plants from becoming deficient. You can do water changes in whatever amount you want and as frequently as you want. Nothing about it is set in stone.
Last edited by Jeff5614; 04-17-2017 at 05:06 PM.