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Dissolved Oxygen & Aeration Calculator

Estimate how much oxygen your fish (and, in a recirculating system, your biofilter) actually consume, and what that means for aeration equipment sizing, from your daily feed rate.

Oxygen demand1.75 kg O₂/day
Required aeration input43.7 m³ air/day

How to measure your inputs

  • Daily feed rate: total kg of feed added per day across your whole stock.

Methodology

Feed-based oxygen demand rule of thumb: ~350g O₂ per kg feed for animal respiration (open systems), rising to ~1kg O₂ per kg feed in recirculating systems once biofilter bacterial respiration is included. Aeration input then divides that demand by the chosen method's dissolution efficiency, accounting for air's ~20% oxygen fraction for diffuser-based systems.

Sizing aeration from what you actually feed, not just fish count

Why feed rate predicts oxygen demand better than fish count

Oxygen consumption tracks metabolic activity, and metabolic activity tracks how much the fish are actually eating and processing — which is why the feed-based rule of thumb (roughly 350g of oxygen consumed per kg of feed) is a practical, widely used way to estimate demand without needing a full bioenergetics model.

Why recirculating systems need almost 3x more oxygen input

In a recirculating system (RAS), the biofilter’s bacteria — which convert toxic ammonia into safer compounds — also consume oxygen, and often consume more than the fish themselves. That’s why total demand in a RAS runs close to 1kg O₂ per kg feed (350g for the fish, roughly 650g for the biofilter), versus 350g alone in an open flow-through system with no biofilter to support.

Why air diffusers need so much more volume than pure-oxygen systems

Regular air is only about 20% oxygen, and diffusers only dissolve a fraction of that into the water — so delivering a given oxygen demand via air diffusers takes a much larger volume than delivering the same demand via a pure-oxygen injector, which skips the 80%-nitrogen dead weight entirely.

Frequently asked questions

How much oxygen does a fish farm actually need?

A commonly used rule of thumb is about 350g of oxygen per kg of feed in an open system, rising to roughly 1kg per kg of feed in a recirculating system once biofilter bacteria demand is included — multiply by your daily feed rate for a working estimate.

Why does my RAS need more aeration than an open pond for the same fish?

A recirculating system’s biofilter bacteria consume significant oxygen converting ammonia into less-toxic compounds — demand that simply doesn’t exist in an open pond where waste disperses into a much larger body of water instead.

What's the difference between air diffusers and pure-oxygen injectors?

Air diffusers push ambient air (about 20% oxygen) through the water with a real dissolution efficiency loss; pure-oxygen injectors deliver concentrated oxygen gas directly, achieving much higher dissolution efficiency per unit of gas — more expensive equipment, but far less volume needed for the same oxygen delivered.

Does water temperature affect oxygen requirements?

Yes significantly — fish metabolism and oxygen consumption roughly double for every 10°C rise in water temperature (within a species’ tolerance range), and warmer water also holds less dissolved oxygen at saturation, compounding the effect. This calculator uses a feed-based estimate that implicitly reflects normal feeding/metabolic activity, but doesn’t separately adjust for extreme temperature swings.