FinsFlora

EI dosing

Estimative Index doses more than plants can use, three times a week, and resets everything with one large weekly water change. You never test for deficiency because there isn't one; the water change caps the build-up. The trade-off is more fertilizer and a mandatory weekly change. Enter your water volume and per-dose targets; this gives you grams and teaspoons for each salt and the week laid out.

Water

Target per dose (ppm = mg/L)

Defaults land inside the commonly cited EI weekly range.1 Set extra K to 0 to skip K2SO4 — KNO3 and KH2PO4 already supply potassium.

Teaspoon calibration & trace mix

Grams are exact. Teaspoons depend on how your salt packs.2 To calibrate: weigh 5 level teaspoons, divide by 5, enter it here.

Each dose

Salt · delivers (ppm)GramsTeaspoons

The week

DayDose

Macros and micros go on different days: phosphate and chelated trace metals can bind each other if dosed together.

Where levels top out

If plants took up nothing, a weekly change of 50% holds each nutrient below this ceiling.3 Real levels are lower.

ppmPer dosePer weekCeiling (before WC)After WC
How this is calculated 
Mass fraction of an ion = its molar mass ÷ the salt's molar mass
  KNO3   101.102 g/mol → NO3 0.61328, K 0.38672
  KH2PO4 136.084 g/mol → PO4 0.69788, K 0.28731
  K2SO4  174.252 g/mol → K 0.44875, SO4 0.55125

ppm = mg/L, so to add P ppm of an ion to V litres:
  grams = P × V ÷ (fraction × 1000)

  g KNO3   = NO3 × V ÷ (0.61328 × 1000)
  g KH2PO4 = PO4 × V ÷ (0.69788 × 1000)
  g K2SO4  = K   × V ÷ (0.44875 × 1000)
  g CSM+B  = Fe  × V ÷ (Fe% ÷ 100 × 1000)

Total K per dose = NO3 × 39.098/62.004 + PO4 × 39.098/94.970 + extra K
NO3 as N (NO3-N) = NO3 × 14.007/62.004
teaspoons = grams ÷ (g per level US tsp)

Ceiling with no uptake: added D ppm/week, fraction f changed weekly.
  Steady state: after = (1 − f)(after + D) → after = D(1 − f)/f
  before = after + D = D/f

Notes

  1. EI targets are a range, not a point. Commonly cited weekly EI levels are about 20–30 ppm NO3, 3 ppm PO4, 20–30 ppm K and 0.5 ppm Fe. The teaspoon charts that circulate for EI work out higher than the defaults here: — That gap is the method working as designed — excess is intentional and the water change is the cap. Choose your own targets; the arithmetic doesn't change.
  2. Teaspoon densities are typical figures, not verified constants. Crystal size, humidity and how level you scrape all move them by 10% or more. Use grams if you own a 0.01 g scale; otherwise calibrate once with the method above.
  3. The ceiling ignores plant uptake, so it's the most that can build up, not a prediction. It assumes one water change of the same size every week.
  4. Trace mix composition. Iron defaults to 6.53%, the Plantex CSM+B label figure. Other elements are scaled from that label (Mn 1.87, Zn 0.40, Cu 0.09, Mo 0.05, B 1.18, Mg 1.50%). If you use a different mix, enter its iron %; the co-delivered figures will only be right for CSM+B.