I just copied this for you from another thread.
As per the Zorfox:
Non limiting nutrient levels are listed below.
CO2 range 25-35ppm
NO3 range 5-30ppm (KNO3)
K+ range 10-30ppm (K2SO4 or GH booster)
PO4 range 1.0-3.0 ppm (KH2PO4)
Fe 0.2-0.5ppm or higher (?) (Plantex CSM +B)
GH range 3 degrees ~ 50ppm or higher (GH Booster)
These are by NO means my numbers. Simply recommendations by Tom Barr. I wrote an article, The EI "Concept" Explained., explaining the idea of non-limiting nutrients with the numbers listed above.
All that said we don't need to "count calories" in our tanks like most suggest. We have three basic systems we keep (this is my interpretation).
High tech; High light and CO2.
Medium tech; Medium light and Excel.
Low tech; low light and no CO2 methods.
You can muddle the waters with variations but they all have basic commonalities.
High tech should receive a full EI dose 2-3 times per week and a 50% weekly water change.
Medium tech should receive about 1/3 full EI and 10% plus weekly water change.
Low tech without water changes is a different animal. Regular water changes? Use the medium tech dosing method. Little to no water changes? Use Tom Barr's Non-CO2 methods.
Mixing solutions to full EI dosing levels is the way to go IMO. For example if you want full EI you dose this 3 times a week. If you want medium tech which is 1/3 EI once a week well...the math ain't so hard. Dose one full EI dose once a week.
The recipe for solutions and dry dosing are listed here,