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API Melafix calculator

API Melafix standard freshwater bottle — not Marine Melafix — US label directions

Read the product guide and worked examples ↓

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API Melafix standard freshwater bottle — not Marine Melafix — US label directions

Choose explicitly; different uses or formulations may have different quantities. Use only the water volume specified for that choice.

Water volume

Actual water amount; no decor deduction.

litres

Supports 3.8–100,000 L after displacement. These are software limits, not livestock safety limits.

Review and calculate

Check the product label, water volume and units.

How calculations work

Calculation inputs stay in this page’s URL so Back and Edit can retain them. Saving tanks or a treatment plan on your device is separate and optional.

Clear amounts. Visible assumptions.

Your calculation, explained

Choose a product and enter the water you’re actually dosing.

  1. Check the exact product and formulation.
  2. Use measured water, or make an explicit estimate.
  3. Review the amount, source and any schedule.
Read our calculation method →

Product guide · edited 28 October 2026

Jump to a section
  1. Which Melafix course is displayed?
  2. Worked examples
  3. Before you measure
  4. Does the calculator identify a bacterial infection?
  5. Sources and next steps

Which Melafix course is displayed?

This is the standard freshwater US bottle, not Marine Melafix. Choose the seven-day diseased/wounded-fish plan or the separate three-day new-fish plan. Each uses the named US reference.

Worked examples

These illustrations use 100 L of measured water, without a decor deduction. Choose the matching stage or formulation above for your own water volume. They do not select a treatment or establish livestock suitability.

Diseased / wounded fish — seven daily doses

StageAmount or action for 100 L
Day 113.21 mL
Day 213.21 mL
Day 313.21 mL
Day 413.21 mL
Day 513.21 mL
Day 613.21 mL
Day 713.21 mL
After seven daysPerform a 25% water change. Reassess before any continuation.

Adding new fish — three daily doses

StageAmount or action for 100 L
Day 113.21 mL
Day 213.21 mL
Day 313.21 mL

Example only. Your calculation above uses your own inputs. Small amounts and powder fractions still need equipment that can measure them reliably.

Before you measure

Shake well and remove activated carbon if possible. The seven-day plan includes a 25% water change afterward. Continuing or changing treatment requires reassessment, not an automatic extra course.

Product-specific checks from the calculation record
  • Shake well and remove activated carbon if possible. This record is for the standard freshwater formulation.
  • Do not confuse a manufacturer-stated use with a confirmed diagnosis or guaranteed outcome.
  • These quantities follow the manufacturer’s US label. If your bottle gives different reference volumes or strengths, use that label and request its specific variant.

Does the calculator identify a bacterial infection?

No. Similar signs can have different causes. Choosing a product and diagnosing illness are separate from calculating the label amount.

Sources and next steps

API manufacturer directions →

Manufacturer page consulted 28 October 2026. Match the exact bottle and leaflet; editorial review does not establish diagnosis or compatibility.

Optional buying links

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API Melafix, 8 fl oz

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Check the selected bottle, formulation and label before buying. These links do not select a treatment or change your dose. Prices, sellers and availability are shown on Amazon. About these links.