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Fish stocking density

See how many fish and how many kilos of live weight there are per cubic meter of pond or tank.

Pre-sizing and estimating tool: the results do not replace a design, calculation, or report signed by a qualified professional, nor verification against the applicable standards.

Preliminary estimateRevision 12/11/2026
Stocking
Volume and target

Usable volume excludes the bottom and freeboard. The default values are examples only.

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—Stocking density
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Biomass per cubic metre according to density

Kilos of fish per cubic meter for densities of 20 to 100 fish/m³, with the batch's average weight; the highlighted bar is yours.

Tap the chart to see the values.

Biomass per cubic metre according to average weight

Kilos of fish per cubic meter with the batch's fish and weights of 0.1 to 1.5 kg; the dot is your batch.

Tap the chart to see the values.

What if the data changes?

Drag the controls to simulate data different from what you entered (from 30% less to 30% more) and watch the result change instantly.

Tap the chart to see the values.

Density and biomass by fish and volume

Biomass, in kg per cubic metre, for densities of 20 to 100 fish/m³ and different average weights.

Step by step with your numbers

The calculation done in steps, with the values you entered.

    The calculation memo gathers this page's inputs, results, equations, assumptions, and references, with fields for project, responsible person, and review. The full report also includes the charts and interpretations, in color. In the print window, choose Save as PDF.

    How to use

    Enter the number of fish stocked, the average weight, the usable water volume, and, if you wish, the target density for the species and system. The calculator shows the density in fish and in kilos per cubic meter, and the number of fish for the target.

    Worked example

    12,000 fish of 80 g in 300 m³ of usable water, with a target density of 50 fish/m³.

    Density = 12,000 ÷ 300 = 40 fish/m³. Biomass = 12,000 × 0.080 ÷ 300 = 3.2 kg/m³. Fish for the target = 50 × 300 = 15,000.

    Precautions

    • Biomass rises over the cycle. A comfortable density at the start can become high by the end: recalculate at a partial harvest.
    • Oxygen and water exchange must track biomass, not fish count. See the pond aeration.
    • For the batch feed, see the daily fish feed.

    Method, assumptions, and references

    Equations used

    Density (fish/m³) = Fish stocked ÷ Usable volume (m³)
    Biomass (kg/m³) = Fish stocked × Average weight (kg) ÷ Usable volume (m³)
    Fish needed for the target = target density (fish/m³) × usable volume (m³)

    Assumptions and limits

    • Usable volume is the water actually available, after deducting the bottom and the freeboard.
    • Average weight is held constant at the check; biomass grows over the cycle.
    • Density limit set by the production system, the species, and the water quality.

    Standards and technical documents

    • Technical husbandry manuals for the species (tilapia, tambaqui, pacu, among others) and recommendations from Embrapa Pesca e Aquicultura (current editions).

    Frequently asked questions

    Which density should I use?

    It depends on the species, the system (pond, net cage, or concrete tank), and the level of aeration and water exchange. Use the species manual's recommendation and your own experience.

    Why does kg per m³ matter more than the number of fish?

    Because it is the biomass that consumes oxygen, produces ammonia and stresses water quality. Many small fish can still have a low biomass.

    Is the volume the same as the water depth?

    Yes, the usable water volume. Subtracting the bottom and freeboard matters, especially in shallow ponds.

    Does the density stay fixed during the cycle?

    No. The number of fish drops with losses and the biomass rises with weight. Recalculate over the cycle.