Dosing & Chemistry
Universal Dosing Calculator
Universal liquid-dosing calculator. Works with any aquarium product - fertilisers, dechlorinators, medications - that lists a dose per a given water volume.
Universal Dosing Calculator
How many mL per unit volume the bottle says to use.
e.g. if the bottle says 5 mL per 50 L, enter 50 here.
Add to your tank
10mL
- Equivalent drops
- 200 drops
- Per 10 L
- 1 mL
~20 drops per mL.
How to scale any aquarium dose
Every liquid aquarium product - fertilisers, dechlorinator, snail treatments, bacterial supplements - is labelled in the form "X mL per Y litres". The dose you need is just a straight ratio:
your dose (mL) = (X / Y) x your tank volume (L)
Worked example
A bottle of Seachem Flourish says "5 mL per 60 L, weekly". For a 120 L tank: (5 / 60) x 120 = 10 mL per week. Split into daily doses, that's 10 / 7 = 1.4 mL per day.
Practical tips
Use a 1 mL or 5 mL oral syringe rather than the bottle cap - they are accurate to 0.1 mL and cost a pound or two. If the product is concentrated enough that your dose would be under 0.2 mL, pre-dilute it (for example 1 mL product into 9 mL tank water) and dose the diluted mixture. For medications, never overdose to "be sure" - most aquarium medications have narrow safe-to-toxic ratios, especially for shrimp, snails and scaleless fish.
Frequently asked questions
How do I read a dosing instruction like "5 mL per 50 litres"?
That means every 50 litres of aquarium water needs 5 mL of product. For a tank of another size, scale proportionally: a 200 L tank needs 4 x the dose, a 25 L tank needs half the dose. This calculator does that scaling automatically.
Should I dose off the total tank volume or the treated volume?
Medication and dechlorinator are dosed off the treated water volume - usually 90% of the nominal tank volume, after subtracting substrate, rocks and equipment. For liquid ferts the difference is small and most people just use the stated tank size.
Can I split a dose across the week?
For most liquid fertilisers (all-in-ones, macro/micro splits), daily dosing is better than weekly because plants use nutrients continuously. Split the weekly dose into 7 daily doses for the smoothest growth and lowest algae risk. For medications, always follow the exact schedule on the bottle.
Why is a small syringe more accurate than the cap?
Bottle caps vary wildly in volume between products and are only accurate to 2-3 mL. A cheap 1 mL, 5 mL or 10 mL oral syringe is accurate to 0.1 mL and makes dosing repeatable. Rinse between products to avoid cross-contamination.
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