Aquarium Fertilizer Calculator is an Android app that tells you how much fertilizer to dose your planted tank, from its volume in liters or gallons. You get grams for EI dry salts or mL for liquid fertilizers, per dose and per week. For example, a 60 L tank on the EI standard preset takes 2.45 g of KNO3 a week, about 0.82 g per dose at 3 doses a week. Log doses, water changes and water tests, follow them on charts and get a reminder for the next dose. Made and published by GRAMSHIFT.
What you can do with Aquarium Fertilizer Calculator
Liquid fertilizer doses in mL
Pick a product and get the dose for your tank from the label dose. Popular products from Seachem, Tropica, ADA, NilocG, Aquarium Co-op, Dennerle, JBL, UNS and more.
EI dry salts in grams per dose
KNO3, KH2PO4, K2SO4 and CSM+B from weekly ppm targets, with teaspoon hints and a stock solution mode. Potassium from KNO3 and KH2PO4 is counted, so K2SO4 only tops up the rest.
CO2 from pH and KH
Estimate CO2 from pH and KH. Values are filled in from your latest water test.
Water tests and doses on one chart
Track pH, GH, KH, NO3, PO4 and temperature with doses and water changes marked. Tank check gives a gentle hint when nitrate is building up or running low.
A growth journal for each tank
Keep dated photos of your aquascape and share them. Livestock and plant notes come with Pro.
Pro: tank report PDF
Pick a period and get water test charts, doses and water changes, fertilizer totals and livestock notes in one PDF.
From tank volume to dose log
- Enter your tank volume. Use liters or gallons. Keep several tanks, each with its own records.
- Pick a fertilizer and see the dose. Choose a liquid fertilizer, your own fertilizer by label dose, or EI dry salts, and see the dose per dose and per week. Presets are EI standard, EI low-tech and PPS-Pro, and every target can be changed.
- Log doses, water changes and tests. Follow them on charts and get dosing reminders at the interval you choose.
Free and Pro
- Free: calculating and logging with no usage limits, plus charts, the growth album, dosing reminders and copying records as CSV. A small banner ad at the bottom of the screen.
- Pro (one-time purchase): backup and restore with photos, tank report PDF, saving records as a CSV file, livestock and plant notes, no ads.
- Remove ads (one-time purchase): removes the banner ad.
- Your records and photos stay on your device unless you send them yourself. No account and no sign-in.
Frequently asked questions
How much KNO3 for EI dosing in a 60 L (16 gallon) tank?
On the EI standard preset (25 ppm NO3 a week), it is 2.45 g a week. That is about 0.82 g per dose at 3 doses a week.
How much liquid fertilizer should I add to my aquarium?
Pick your product and enter your tank volume to get the dose in mL. A label dose of 5 mL per 250 L becomes 2 mL for a 100 L tank.
Does it work for a low-tech tank without CO2?
Yes. Use the EI low-tech or PPS-Pro preset, or your liquid fertilizer's dose.
How do I estimate CO2 from pH and KH?
Enter pH and KH in a water test and the app estimates CO2. The values are filled in from your latest test.
Can I move my records and photos to a new phone?
Yes. Pro backup & restore puts your tanks, logs, fertilizers, settings and album photos in one file.
Is the fertilizer calculator free?
Yes. Calculating and logging are free with no usage limits. Backup, the tank report PDF, CSV files and livestock notes come with Pro, a one-time purchase.
Do I need an account?
No. Start without signing up.
Good to know
- Doses are estimates from label doses and standard formulas. Read the product label and test your water.
- Teaspoon amounts are approximate. For small amounts, use a scale.
- The CO2 estimate reads high when soil, driftwood or pH products lower the pH.
- Records and photos stay on your device. Moving them to another device needs Pro backup.
- For planted aquariums only. Not for medical or veterinary use.
- Product and brand names are trademarks of their owners. This app is independent and not affiliated with any manufacturer.
If something does not work, or you have an idea or a request, feel free to write to us through the contact form or at contact