Free EI Dosing Scheduler - Planted Tank Fertilizer Calculator | Fish Tank Calculator

Calculate weekly EI (Estimative Index) fertilizer doses for your planted aquarium. Scaled to your tank volume with a full Mon–Sun schedule: macros, micros, and water change day.

The Estimative Index (EI) is the dominant fertilization protocol for high-tech planted aquariums because it removes guesswork: nutrients are dosed in excess, weekly water changes reset accumulation, and plants never see deficiency. This calculator scales the standard EI recipe to your specific tank volume in liters or gallons and outputs the per-dose macro (KNO3, KH2PO4), micro (Plantex CSM+B), and water-change schedule needed to follow EI without home-blending mistakes.

How It Works

Standard EI targets approximately 10-30 ppm NO3, 1-3 ppm PO4, and 10-30 ppm K weekly, distributed across three macro doses and three micro doses with a single 50% water change to reset accumulation. The calculator scales these targets to your reported tank volume, returns per-dose grams for KNO3, KH2PO4, and trace mix, and lays out a Monday/Wednesday/Friday macro schedule with Tuesday/Thursday/Saturday micro doses, finishing with a Sunday water change.

Usage Scenarios

  • Switching a 200-liter high-tech planted tank from a commercial all-in-one fertilizer to dry salts and saving roughly 70% on annual fertilization cost.
  • Adapting EI to a smaller 60-liter shrimp-and-plant tank where standard doses must be cut to avoid stressing Crystal Red colonies.
  • Following EI on a heavily planted 90 cm Dutch layout with daily CO2 injection and high light where weekly 50% changes are essential.
  • Transitioning back from PPS-Pro lean dosing to EI when adding additional high-demand stems like Rotala macrandra or Ludwigia pantanal.

How to Use the EI Dosing Scheduler

Enter your tank volume in liters or gallons. The calculator scales standard EI doses proportionally to your tank size. EI (Estimative Index) uses deliberately high nutrient doses to prevent deficiencies.

Macros (KNO₃, KH₂PO₄, K₂SO₄) are dosed three times per week on Monday, Wednesday, and Friday. Micros (trace elements) are dosed on Tuesday, Thursday, and Saturday.

A 50% water change every Sunday resets the nutrient baseline and prevents salt buildup. This weekly reset is what makes the EI method work — it replaces the need for precise testing.

Frequently Asked Questions

What is the EI (Estimative Index) method?

EI was developed by Tom Barr to remove the need for daily nutrient testing. You dose deliberately above plant demand so nutrients are never limiting, then perform a 50% water change weekly to reset and prevent buildup. The result is fast plant growth without algae from imbalance.

Do I need to test water with EI?

No — that is the whole point. The weekly 50% water change resets nutrient levels regardless of plant uptake. Some advanced aquarists test occasionally to fine-tune for very high or very low light setups, but it is not required for the standard schedule.

Why a 50% water change every Sunday?

Even with deliberately high dosing, nutrients accumulate over the week. A 50% change brings everything back to roughly half — preventing extreme buildup of any single element while still leaving plants well-fed. Skipping the change is the most common cause of EI failure.

Can I dose macros and micros together?

No — they react and precipitate. Iron from micros binds with phosphate from macros and falls out of solution as an insoluble compound. Always alternate days: macros on Mon/Wed/Fri, micros on Tue/Thu/Sat, water change on Sunday.

Will EI cause algae?

EI does not cause algae directly — algae outbreaks during EI come from poor CO2 distribution, low CO2, or insufficient light spread. EI provides excess nutrients so plants outcompete algae. If algae appears, check CO2 first, then flow and light, before adjusting fertilizer.