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Tank Mix Order Planner.
Tank Mix Order Planner
Order matters. Calcium nitrate and a phosphate dropped into water together precipitate; phosphate plus magnesium does the same. Plan the sequence.
The universal mixing rules
- Never mix dry concentrates directly. Always dilute in water first.
- Never combine calcium and phosphate or sulfate at high concentration. Calcium phosphate (insoluble) and calcium sulfate (gypsum, low solubility) precipitate immediately.
- Never combine calcium with magnesium phosphate. Magnesium phosphate is similarly low-solubility.
- Always pH the water first. Then add nutrients. Then verify final pH and adjust again.
- Add chelates after micros. The chelating agent (EDTA, DTPA, EDDHA) needs to grab the metal in solution.
- Add silicate (potassium silicate / Pro-TeKt) FIRST to alkaline-stable water. Silicates precipitate in acidic water — they raise pH significantly.
- Always agitate while adding each component, and let each dissolve before the next.
- Surfactant / wetting agent goes LAST in foliar tanks, otherwise it foams.
Two-tank A/B concentrate scheme
The classic hydroponic concentrate pattern keeps calcium separate from sulfate and phosphate. At 100×-200× concentration these MUST be separated; once diluted into the final feed, they coexist fine.
| Tank A (Calcium-side) | Tank B (Phosphate/Sulfate-side) |
|---|---|
| Calcium nitrate Ca(NO₃)₂ | Monopotassium phosphate KH₂PO₄ (MKP) |
| Potassium nitrate KNO₃ | Magnesium sulfate MgSO₄ (Epsom) |
| Iron chelate (FeEDTA / FeDTPA) | Potassium sulfate K₂SO₄ |
| (some recipes) Manganese chelate | Trace mix (Mn, Zn, Cu, B, Mo) |
| Ammonium nitrate (acid recipes) | Boric acid H₃BO₃ |
Key: calcium and iron go in Tank A. Phosphate, sulfate, magnesium, and trace metals go in Tank B. Acid (nitric or phosphoric for pH) is usually a Tank C, kept separate from both. They all converge into the final feed at proper dilution and the final solution is stable.
Why precipitates matter
- Calcium phosphate (Ca₃(PO₄)₂): White cloudy precipitate. The calcium and phosphate both come out of solution — neither is plant-available.
- Calcium sulfate (CaSO₄ / gypsum): Solubility is only ~2.4 g/L at 20°C. At concentrate strength, instant haze.
- Iron oxidation: Non-chelated iron oxidizes to Fe³⁺ and precipitates as ferric oxide / hydroxide. This is why we use chelates (EDTA, DTPA, EDDHA) — they keep iron available across pH ranges.
- Calcium carbonate scale: High-Ca + high-pH water deposits limescale on emitters and pumps. Acidify first.
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