Tool
Dosing calculator
Turn a "mL per 10 L" label into the exact dose for your tank.
Your result
Add about 50 mL
That is 5 mL for every 10 L of tank water.
What this calculator does
Medicines, water conditioners and fertilisers are almost always labelled as a dose per volume — for example "5 mL per 10 litres". This tool scales that to your actual water volume, so you add the right amount instead of guessing. Getting the volume right first matters, because the dose is proportional to it.
When to use it
- Treating a tank with medicine.
- Adding a water conditioner at a water change.
- Dosing plant fertiliser.
How to use it
- Find the real water volume, not the nominal tank size.
- Read the label for the dose and the volume it refers to.
- Enter both and measure out the result with a syringe or measuring cap.
Worked example
A product dosed at 5 mL per 10 L, used in a 100-litre tank, needs 50 mL. In a 54-litre tank the same product needs about 27 mL — which is why dosing to the "100 litre" number on the box of a smaller tank would overdose it.
Limitations
- Follow the label. Some medicines dose once, some over several days, and some are reduced for sensitive fish.
- Some products dose to the whole tank, some to the water changed. Read the label carefully.
- Do not mix treatments without checking compatibility.
Frequently asked questions
Do I dose by tank size or water changed?
It depends on the product. Water conditioners often dose to the volume replaced; many medicines dose to the whole tank volume. Check the label.
How accurate must the volume be?
Close is usually fine, but for medicines it is worth using the real water volume rather than a rounded nominal tank size.
Can I overdose fertiliser?
Yes — too much can feed algae or harm livestock. Start at the label rate or below and adjust gently.
Related guides
Sources and research notes
Doses are always set by the product label; this tool only scales the stated rate to your volume.