EI Dosing Complete Guide: Estimative Index for Planted Tanks

This EI dosing complete guide planted tank resource explains the Estimative Index method from first principles to practical application. At Gensou Aquascaping, based at 5 Everton Park, Singapore, we use EI dosing as a reliable foundation for high-tech planted aquariums and have helped many local hobbyists implement it successfully.

What Is EI Dosing

The Estimative Index, developed by Tom Barr, is a fertilisation method based on a simple principle: provide nutrients in excess so that plants never experience a deficiency, then reset the system with a large weekly water change to prevent excessive accumulation. Unlike lean dosing methods that aim to supply only what plants consume, EI eliminates the guesswork by ensuring all essential nutrients are always available. This approach works because healthy plants in a well-lit, CO2-enriched tank consume nutrients rapidly, and the weekly water change prevents any single element from building to harmful levels.

Essential Chemicals and Sources

EI dosing uses dry fertiliser salts, which are far more cost-effective than commercial liquid fertilisers. The core chemicals are potassium nitrate (KNO3) for nitrogen and potassium, monopotassium phosphate (KH2PO4) for phosphorus, potassium sulphate (K2SO4) for additional potassium if needed, and a comprehensive trace mix such as CSM+B or a similar micronutrient blend that includes iron, manganese, boron, zinc and copper. These dry salts are available from aquarium suppliers and chemical retailers in Singapore. Store them in airtight containers away from moisture to maintain potency.

Standard Dosing Schedule

The classic EI schedule alternates between macronutrient and micronutrient dosing days across the week. For a typical high-light, CO2-injected tank of approximately 200 litres, the standard regimen is as follows. On days one, three and five, dose macronutrients: approximately one-quarter teaspoon of KNO3 and one-sixteenth teaspoon of KH2PO4. On days two, four and six, dose micronutrients: approximately one-sixteenth teaspoon of trace mix. On day seven, perform a 50 per cent water change to reset nutrient levels. These quantities are starting points; adjust based on your specific tank volume, plant mass and growth rate.

Making Stock Solutions

Many aquarists prefer to dissolve dry salts into liquid stock solutions for easier and more precise dosing. To prepare a macro solution, dissolve the weekly quantity of KNO3 and KH2PO4 in 250 to 500 millilitres of distilled or RO water. For the micro solution, dissolve the weekly trace mix quantity in a separate 250 to 500 millilitres of water. Dose the appropriate amount from each bottle on the designated days. Keep macro and micro solutions in separate bottles, as combining them can cause precipitation. Store solutions in the refrigerator if not used within two weeks, particularly in Singapore’s warm climate, to prevent bacterial growth.

The Role of CO2 and Light

EI dosing is designed for high-tech planted tanks with strong lighting and pressurised CO2 injection. Without adequate CO2, plants cannot utilise the nutrients provided, leading to excess nutrients in the water column that fuel algae growth. Maintain CO2 at 20 to 30 ppm throughout the photoperiod, verified with a calibrated drop checker. Lighting should deliver at least 50 to 80 micromoles of PAR at the substrate level. In Singapore, where many aquarists run high-output LED units, ensuring CO2 keeps pace with light intensity is the most critical balance to maintain.

Adjusting for Your Tank

The standard EI values are guidelines, not rigid prescriptions. Heavily planted tanks with fast-growing stems may require increased dosing, while tanks with slower-growing species like Anubias and Bucephalandra may need less. Observe your plants for signs of deficiency or excess. Nitrogen deficiency presents as yellowing of older leaves, while phosphorus deficiency causes dark or purplish discolouration. Iron deficiency shows as pale new growth. If algae appears despite consistent dosing, the issue is almost always related to insufficient CO2 or poor CO2 distribution rather than excessive nutrients. Adjust one variable at a time and observe for two weeks before making further changes.

Weekly Water Changes

The 50 per cent weekly water change is a non-negotiable component of EI dosing. It serves two purposes: resetting accumulated nutrient levels to prevent toxicity and removing organic waste that degrades water quality. In Singapore, treat replacement water with a dechlorinator and match the temperature to the tank before adding it. If your tap water has significantly different parameters from your tank water, add the replacement water gradually to avoid shocking sensitive species. Some aquarists perform the water change the evening before restarting the dosing cycle on day one.

Getting Started with EI in Singapore

EI dosing is one of the most reliable fertilisation methods for planted aquariums, and its simplicity makes it accessible to hobbyists at all levels. Start with the standard dosing amounts, maintain consistent CO2 and light, and perform faithful weekly water changes. Dry fertiliser salts are available from several aquarium supply shops and online sellers in Singapore, often at a fraction of the cost of branded liquid fertilisers. Visit Gensou Aquascaping at 5 Everton Park for personalised guidance on setting up an EI dosing regimen tailored to your specific tank, plant selection and goals.

Related Reading

• How to Set Up Auto Dosing for Your Planted Aquarium
• Glutaraldehyde in Aquariums: Liquid Carbon and Algae Control
• Iron Dosing in Planted Aquariums: Red Plants Need It Most
• Lean Dosing Method for Planted Aquariums: Less Is More
• Nitrogen Dosing in Planted Aquariums: The Primary Macro