Calculate daily oxygen demand and hourly injection rate for RAS aquaculture systems based on daily feed input and fish species (salmonid, tilapia, carp).
Dissolved oxygen is the most under-monitored, fastest-killing parameter in aquariums and aquaculture. Fish consume oxygen continuously, and their consumption rate is tied to feeding rate, species, and water temperature. This calculator estimates daily oxygen demand in kilograms and grams per hour from feed mass and species type, helping you size aerators, surface skimmers, and oxygen-injection systems before a summer heatwave or power outage triggers a fish kill.
The standard relationship uses an oxygen consumption coefficient per kilogram of feed: salmonids burn roughly 0.22 kg O2 per kg of feed, tilapia roughly 0.20, and carp around 0.18 under standard conditions. Multiplying daily feed mass by the species coefficient gives daily oxygen demand. Dividing by 24 gives the hourly figure used to spec aerators or pure-oxygen injection. Real demand spikes after feeding and at temperatures above 26 degC, so a safety factor of at least 1.5 is recommended.
Enter daily feed amount and select your fish species. The calculator multiplies feed by an oxygen coefficient (1.0 for salmonids, 0.75 for tilapia, 0.65 for carp) to estimate daily O₂ consumption.
Divide by 24 to get the hourly injection requirement. Size your oxygen generator or LOX supply to at least this rate, plus 30% headroom for post-feeding peaks and transfer losses.
Measured DO should stay above 6 mg/L for salmonids and 4 mg/L for warm-water species. If DO drops, reduce feeding or increase aeration — do not raise pure oxygen injection without a degassing tower.
Cold-water salmonids (trout, salmon) consume roughly 1.0 g O₂ per gram of feed. Tilapia and warm-water species are around 0.75. Carp and other slower metabolisms are closer to 0.65. Using the wrong coefficient can under- or oversize your oxygen system by 30%.
Salmonids need 6 mg/L minimum, ideally 8+ mg/L. Tilapia tolerates 4 mg/L but performs better above 5. Shrimp systems need 5+ mg/L. Below 4 mg/L most species show stress; below 2 mg/L is critical and usually fatal within hours.
Small systems use air diffusers (raises DO toward saturation, ~8 mg/L at 25°C). Larger or denser systems require pure oxygen injection through cones, U-tubes, or low-head oxygenators that can push DO well above saturation. Above-saturation oxygen is essential for high stocking density.
Fish consume more oxygen 1–4 hours after feeding (specific dynamic action). Stress from handling, transfer, or temperature spikes can also raise demand briefly. Sizing 30% above average ensures the system holds DO during these peaks instead of crashing.
Fish gasp at the surface and stop feeding. Below 2 mg/L most species suffocate within hours. Reduce feeding immediately, increase aeration, and check pump/oxygen supply. Long-term low DO also impairs nitrification — biofilter ammonia removal drops sharply below 4 mg/L.