# Aquaculture Dissolved Oxygen Demand Calculator

> Estimate how much oxygen a fish stock consumes from its biomass and consumption rate, the water flow that would supply it, and the aerators needed.

Category: Agriculture · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/aquaculture-dissolved-oxygen-demand-calculator

Fish oxygen use is biomass times a consumption rate. To keep up, inflowing water must carry that much oxygen above your minimum level, or aerators must add it.

Also called: Fish oxygen consumption calculator, Aerator requirement calculator.

## Inputs
- Fish biomass (unit kg; default 2000)
- Oxygen consumption rate (unit mg O₂ per kg fish per hour; default 300)
- Dissolved oxygen of inflow water (unit mg/L; default 8)
- Minimum dissolved oxygen to keep (unit mg/L; default 5)
- Oxygen added per aerator (field rate) (unit kg O₂/h; default 0.5; optional)

## Results
- Oxygen demand
- Oxygen demand
- Water flow to supply it
- Water flow to supply it
- Water flow to supply it
- Aerators needed

## Formula

```
Demand (mg/h) = Biomass × Rate;  Flow (L/h) = Demand ÷ (DO_in − DO_min);  Aerators = ⌈Demand (kg/h) ÷ Aerator rate⌉
```

Where:
- Rate: mg of oxygen used per kg of fish per hour
- DO_in: oxygen in the incoming water, mg/L
- DO_min: lowest oxygen level you will allow in the tank or pond

## Worked example
1. Demand = 2,000 kg × 300 mg/kg/h = 600,000 mg/h = 600 g/h, or 14.4 kg a day.
2. Each litre of inflow can give up 8 − 5 = 3 mg, so flow = 600,000 ÷ 3 = 200,000 L/h = 200 m³/h.
3. Aerators: 0.6 kg/h ÷ 0.5 kg/h = 1.2, so 2 aerators.

**Result:** Two tonnes of fish using 300 mg/kg/h need 14.4 kg of oxygen a day: 200 m³/h of water flow or two 0.5 kg/h aerators.

## What the result means

Oxygen use peaks after feeding and at high temperature, and ponds lose oxygen to algae and sediment at night. Size aeration for the worst hours, not the daily average.

## Assumptions and limits
- Consumption rate is constant over the period.
- The fish are the only oxygen consumer.
- Pond respiration by plankton and sediment, and oxygen added by photosynthesis, are not included.

## Questions

### Where do I get the oxygen consumption rate?

From research or extension data for your species at your water temperature and fish size, or from your equipment supplier. Small fish use more oxygen per kg than large fish.

### Why is the aerator rating reduced?

Makers rate aerators in clean water with zero oxygen. In a stocked pond, transfer is lower, so use a field figure rather than the standard rating.

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Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/aquaculture-dissolved-oxygen-demand-calculator