EI Dosing Calculator
Calculate Estimative Index fertilizer doses for your planted aquarium. Get exact amounts of dry salts for optimal plant growth.
Tank Setup
Dosing Method
For high-light, CO2-injected tanks
Per Dose (3x weekly)
Weekly NO₃
30 ppm
Weekly PO₄
3 ppm
Weekly K
30 ppm
Weekly Fe
0.5 ppm
Weekly Totals
EI Dosing Schedule
EI Method Notes
- • EI deliberately overdoses nutrients so plants never run out
- • Large weekly water change resets nutrient buildup
- • Best for high-light, CO2-injected planted tanks
- • Reduce doses for low-light or non-CO2 setups
- • Watch for algae if light/CO2 doesn't match fert levels
Understanding the EI Method
The Estimative Index, developed by Tom Barr, takes a different approach to planted tank fertilization: instead of testing and targeting specific levels, you ensure plants always have more nutrients than they need.
The EI Philosophy
- Overdose during the week: Nutrients never limit growth
- 50% water change weekly: Resets levels, prevents accumulation
- No testing required: Levels stay in safe range by design
- Focus on CO2 and light: These become the limiting factors
Standard EI Target Levels (ppm/week)
NO₃ (Nitrate)
PO₄ (Phosphate)
K (Potassium)
Fe (Iron)
Dry Fertilizer Sources
Macros
- KNO₃: Nitrate and potassium
- KH₂PO₄: Phosphate and potassium
- K₂SO₄: Additional potassium if needed
- MgSO₄: Magnesium (Epsom salt)
Micros
- CSM+B: Complete trace mix (Fe, Mn, Zn, B, Cu, Mo)
- DTPA Fe: Chelated iron for low pH tanks
- Or commercial trace products
Dry salts can be purchased from aquarium specialty vendors or hydroponics suppliers. A few dollars worth of dry ferts can last a year for most tanks.
Frequently Asked Questions
What is the Estimative Index (EI) method?
EI is a fertilization method that provides excess nutrients to ensure plants never run out. You dose more than plants need during the week, then perform a large water change (50%) to reset nutrient levels. This eliminates deficiencies without precise testing.
Do I need CO2 injection for EI dosing?
Standard EI is designed for high-light, CO2-injected tanks where plants grow fast and need lots of nutrients. For low-light or non-CO2 tanks, use 'EI Low Light' which doses at half the standard rate. Too many nutrients without enough light/CO2 promotes algae.
Why dose macros and micros on alternating days?
Some believe phosphate can precipitate iron if dosed together, though this is debated. Alternating days is traditional EI practice. Many successful aquarists dose everything together without issues. The key is consistency and regular water changes.
What's the difference between dry salts and liquid fertilizers?
Dry salts (KNO3, KH2PO4, etc.) are much more economical - often 10-20x cheaper per dose than commercial liquids. They require a scale and mixing but last much longer. This calculator provides grams needed for dry salts.
Why is my tank still getting algae with EI?
Algae in EI tanks usually indicates a CO2 or light issue, not nutrients. Check CO2 levels (aim for 30ppm), ensure consistent CO2 during photoperiod, verify light isn't too intense, and maintain the 50% weekly water change. Also check for ammonia spikes.
Can I use EI in a shrimp tank?
Yes, but some shrimp are sensitive to copper in trace mixes. Use a shrimp-safe trace mix or dose at lower levels. The macros (NPK) are fine for shrimp. Many breeders successfully run planted shrimp tanks with modified EI dosing.
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