Why Standard Fertilisers Do Not Replace Remineralisation
Unstable pH: without KH, any micro-addition of acid sends pH from 7.0 to 4.5 — there is no buffer. In RO water, pH swings are abrupt and uncontrollable.
Ca and Mg deficiency: a standard fertiliser recipe is calculated for water with GH 6–8°dH (50–70 mg/L Ca already present in the source water). RO water has no background Ca or Mg.
Correct sequence: remineralise first → then mix the fertiliser recipe.
What a Mineralising Concentrate Must Contain
Ca and Mg: target ratio Ca:Mg = 3:1–4:1 (for example, 120 mg/L Ca and 35 mg/L Mg).
Buffer component (KH): carbonates/bicarbonates → KH 2–4°dH. Without a buffer, pH remains unstable even after remineralisation.
Micronutrients: some concentrates include Fe, Mn, Zn. When used alongside a full fertiliser recipe, this may result in excess.
Verification After Remineralisation
Target parameters before mixing the fertiliser recipe:
- GH 4–6°dH
- KH 2–4°dH
- EC 0.2–0.4
Stability test: adjust pH to 6.0 and recheck after 30 minutes. Deviation >0.3 → KH is insufficient.
Three Mistakes That Cost the Most
- Remineralising by feel without measuring — RO water quality changes as the membrane degrades
- Using CalMag fertiliser instead of a mineralising concentrate — it supplies Ca and Mg but does not provide KH buffering
- Not recalculating the recipe after switching to RO — the switch always requires a full recipe recalculation
Signs of a Correct Setup
- pH 5.8–6.2, deviation ≤0.15 over 12 hours without plants
- EC matches the target value
- No Ca/Mg deficiency symptoms in the first two weeks