Planted Tank
Fertilizer
EI method dosing for KNO3, KH2PO4, and micronutrients.
Doses are dry salts (KNO₃, KH₂PO₄, K₂SO₄) split across the week. Use a 0.01 g scale. Commercial all-in-ones can replace dry salts — follow that product's label instead.
Per-dose dry salts
KNO₃ (nitrate)
1.64g / dose
KH₂PO₄ (phosphate)
0.18g / dose
K₂SO₄ (potassium)
1.37g / dose
Doses / week
3/ 50% WC
Classic EI: non-limiting macros with a 50% weekly water change. Ideal for high-light planted tanks with pressurized CO2.
Dose a comprehensive micros mix (e.g. CSM+B / commercial micros) 2–3× weekly on alternate days from macros, or use a combined all-in-one per label.
How to use this
- Confirm water volume with the Tank Volume tool (decor and substrate reduce gallons).
- Choose lean, standard, or heavy based on light and CO₂ — not on how fast you want magic growth.
- Weigh salts per dose on a milligram/0.01 g scale; dissolve in a dosing bottle of tank water if you prefer liquids.
- Dose macros on schedule, micros on alternate days, and do the listed large weekly water change to reset the tank.
Weekly targets (then ÷ doses)
- Lean ≈ NO₃ 10 · PO₄ 1 · K 10 ppm/week
- Standard ≈ NO₃ 20 · PO₄ 2.5 · K 20 ppm/week
- Heavy ≈ NO₃ 30 · PO₄ 3.5 · K 30 ppm/week
Standard EI — grams per dose (3× weekly)
Weigh on a 0.01 g scale. KNO₃ already supplies some potassium; K₂SO₄ fills the rest. Pair this with a 50% weekly water change or the tank accumulates.
| Tank | KNO₃ | KH₂PO₄ | K₂SO₄ |
|---|---|---|---|
| 10 gallon | 0.41 g | 0.05 g | 0.34 g |
| 20 long | 0.82 g | 0.09 g | 0.68 g |
| 29 gallon | 1.19 g | 0.13 g | 0.99 g |
| 40 breeder | 1.64 g | 0.18 g | 1.37 g |
| 55 gallon | 2.26 g | 0.25 g | 1.88 g |
Worth knowing
- If algae explodes, cut light hours first — EI assumes plants can use the nutrients.
- Shrimp-heavy tanks often prefer leaner dosing and gentler water-change swings.
- Pre-mix a week of doses in RO/distilled water with a drop of acid (for micros) following hobby recipes carefully.
Usual mistakes
- Dosing EI without CO₂ and strong light — nutrients then feed algae.
- Skipping the big weekly water change that EI is built around.
- Confusing teaspoon estimates with gram doses — scales matter.
See also: CO₂ · Lighting · Water Change