Using Ei Dosing For Hydroponics


Junior Poster
Mar 31, 2008
Slightly off topic but I have been using EI dosing for years with great success. I'm trying to take a step in a different direction namely kratky hydropnics

It requires masterblend fertilizer which is an NPK of 4-18-38 which made me think. I have pounds and pounds of dry ferts for my EI dosing so I should be able to get that ratio as well if I paid more attention in chemistry class. So I'm wondering what is the NPK of ei dosing?

Can I modulate ei dosing into the 4-18-38 ratio? If so can someone point me in the right direction to do the math for it.

Then finally has anyone used EI dosing for hydroponics instead?



Lifetime Member
Lifetime Member
Jun 3, 2013
Nothing wrong with using ei type ferts for hydroponics. The 4-18-38 is just a ratio of npk. Typically these ferts would be supplemented with calcium nitrate and magnesium sulphate to bring the nitrogen, calcium, magnesium, and sulphur levels up, so consider what the manufacturer reccommends adding to it in your calculations. Also if your water is very hard or has high nitrates, you can adjust your mix for that as well. The finished ratio may be closer to 36-18-38. The math is a bit beyond my brain capacity right now, but there are calculators out there to help, including the fert calculators on this site. The calculations are the same as for a fish tank, just higher overall ppm’s for hydro.