EI Dosing Explained: A Simple Fertilizer Schedule for Planted Tanks

EI dosing, short for Estimative Index, is a planted-tank fertilizer method where you add a deliberate surplus of nutrients each week, then reset it with a large water change. The idea is to keep plants from ever running short, so you never have to test and chase numbers.

How EI dosing works

You dose macronutrients (nitrogen, phosphorus, potassium) on some days and micronutrients (trace elements and iron) on others. The amounts intentionally overshoot what the plants use.

At the end of the week a 50 percent water change flushes the excess, so nutrients never build to harmful levels. That weekly reset is the whole safety mechanism.

A simple weekly schedule

A common rhythm splits the week into macro days and micro days with a rest day, then a big water change to close it out.

• Day 1: 50 percent water change, then dose macros
• Days 2 and 4: dose micros
• Days 3 and 5: dose macros
• Days 6 and 7: rest, light dosing optional

Dry fertilizers are cheapest, but premixed liquids work the same way if you prefer convenience. This approach pairs naturally with a proper planted tank setup.

Do you actually need it

EI shines in high-light, CO2-injected tanks where plants grow fast and eat a lot. A slow, low-tech tank rarely needs that much.

If most of your plants are root feeders, root tabs may serve you better than heavy water-column dosing. Our breakdown of root tabs vs liquid ferts helps you decide.

Watch for algae, not just growth

Excess nutrients alone do not cause algae, but an imbalance between light, CO2, and ferts often does. If green starts creeping in, look at your CO2 and light before you blame the fertilizer.

Learning to read the early signs helps, so keep our guide to the types of aquarium algae handy. Dial the dose to your tank, watch how plants respond, and adjust in small steps.