AquaPulse Tools · Free web calculator
Planted Aquarium Fertiliser Calculator
Scale your fertiliser's own label dose to your actual tank volume and a weekly schedule. This tool does arithmetic only — it doesn't recommend a product, a nutrient target, or a dosing philosophy for you. Runs entirely in your browser — no login, no account, nothing saved or sent anywhere.
Planted aquarium fertiliser dose calculator
Before you use this: always follow your fertiliser manufacturer's full instructions. Whether a given dose and frequency actually suits your plants depends on your light, CO2, stocking and current nutrient levels — see our planted aquarium fertilising guide for that decision. This calculator cannot judge any of that; it only scales the numbers you enter.
Your results
What this calculator is — and isn't
This is a narrow safety tool with one job: turning "the label says X amount per Y litres or gallons" into the equivalent amount for your own tank's actual volume, correctly and consistently, then multiplying by however many times a week you dose. It doesn't hold a database of fertilisers, nutrient concentrations or plant-specific targets, and doesn't decide whether a product, dose or frequency is right for your plants, livestock or CO2 setup.
All of that stays with your product's own manufacturer instructions, and with our planted aquarium fertilising guide if you're deciding between an All-in-One and Estimative Index approach. If your plants are already showing a specific symptom, our nutrient deficiency guide is a better starting point than this calculator.
Common fertiliser-dosing mistakes
- Estimating tank volume from tank dimensions in your head. Confirm your actual volume with our Aquarium Calculator first — substrate, décor and water level all reduce it below the tank's nominal size.
- Applying a different product's label dose to yours. Nutrient concentration genuinely varies between brands and formulations — always use your own product's own label.
- Scaling a heavy-dosing schedule (built for a high-light, CO2-injected tank) onto a low-tech setup without adjusting frequency, overshooting what a slower-growing tank can use.
- Increasing dose or frequency to fix poor growth without first checking whether light or CO2 is the actual limiting factor.
- Forgetting the water change an Estimative Index schedule depends on, letting nutrients accumulate past the schedule's intended reset point.
How AquaPulse helps
Getting today's dose right is one calculation. Noticing whether a dosing routine is actually working — whether growth this month genuinely looks better than last month — is a different problem, and it's the one that's hard to answer from memory alone once a routine becomes habitual.
AquaPulse works from what you enter — it doesn't dose your tank or track plant growth automatically. Logging your dosing changes and notes in AquaPulse alongside your regular water testing keeps that record in one place, so you're tracking against what you actually did, not against a vague impression. Get AquaPulse on the App Store or Google Play to try it.
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Related tools and guides
Common questions
Frequently asked questions
Does this calculator tell me which fertiliser to use or how often to dose?
No. This tool doesn't know what any fertiliser is, doesn't recommend a product, and doesn't hold nutrient targets for any plant. It performs one calculation: scaling the dose your product's own label states to your actual tank volume, and multiplying that by a dosing frequency you choose. Choosing a fertiliser, a target nutrient level, and a dosing philosophy (All-in-One or Estimative Index) is covered in our planted aquarium fertilising guide, not this calculator.
Why isn't there a dropdown to pick my fertiliser brand?
Deliberately. This calculator doesn't hold a database of fertiliser products, nutrient concentrations or doses, and never will — concentration genuinely varies between brands and formulations, and presenting a fixed figure for a named product would risk being wrong or outdated. Instead, you enter the dose and reference volume printed on your own product's label, and the calculator scales that to your tank.
Is it safe to fertilise based on this calculator alone?
This calculator only checks your arithmetic — it doesn't check whether the product, dose or frequency is appropriate for your plants, livestock or CO2 setup. Always read your product's full manufacturer instructions, and see our planted aquarium fertilising guide if you're not yet sure which dosing approach suits your tank.
Can I use this for both All-in-One and Estimative Index dosing?
Yes — the underlying arithmetic (scaling a label dose to your tank volume) is the same regardless of which dosing philosophy you're following. For Estimative Index dosing, run the calculator separately for each individual macro or micronutrient product you're dosing, using that product's own label and your own schedule.
How this calculator works: the result is your label dose amount, multiplied by (your tank volume ÷ the label's reference volume), then multiplied by your chosen doses-per-week for a weekly total — pure ratio scaling, with no fertiliser-specific data built in. Volume unit conversions use exact published constants (1 US gallon = 3.785411784 litres, 1 UK gallon = 4.54609 litres). Nothing you enter is saved or sent anywhere.
What we deliberately left out: any list or database of fertilisers, nutrient concentrations or brand-specific doses; any suggestion of which product or dosing philosophy to use; and any default dosing frequency — all of that depends on your specific product, plants and setup in ways this calculator isn't positioned to judge.
Sources and editorial information
- Published
- 8 August 2026
- Last reviewed
- 8 August 2026
- Written and maintained by
- AquaPulse (Valeon Labs Ltd)
This calculator and its supporting content are written and maintained by the AquaPulse team at Valeon Labs Ltd. The arithmetic uses only the figures you enter from your own product's label and your own tank's volume — there is no built-in fertiliser or nutrient data of any kind. We'll update this page if we find something we've got wrong.
Good to know: This tool provides arithmetic assistance only. It is not a substitute for your product's own manufacturer instructions or our planted aquarium fertilising guide, and it does not recommend a dose, product or schedule for your specific tank.