Pond Biomedia Calculator
How much biological media your pond actually needs — based on what you feed and how warm the water is.
72 °F
Media required
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Daily feed—
Ammonia load (TAN)—
KH burned per week—
O₂ saturation limit—
How this is calculated
- Ammonia from feed. TAN (g/day) = feed × protein% × 0.092. That factor is the standard aquaculture value from Timmons & Ebeling: protein is 16% nitrogen, roughly 80% is assimilated, 80% of that is excreted, and 90% of it leaves as ammonia rather than urea.
- Media sizing. Volume = ammonia load ÷ (areal removal rate × specific surface area), multiplied by your safety factor.
- Temperature. Nitrifying bacteria slow down badly in cold water. Rates are corrected with the standard Arrhenius factor of 1.08 per °C, referenced to 68 °F. At 50 °F your filter works at roughly 40% of its summer speed.
- Feed estimate. Leave the feed field blank and we estimate from fish weight: 3% of body weight per day above 70 °F, tapering to 0.5% at 41 °F. Below 41 °F koi generally stop taking food. If you know what you actually feed, enter it — it is always more accurate than an estimate.
- Alkalinity. Nitrification consumes 7.14 g of alkalinity as CaCO₃ for every gram of ammonia processed. This is why KH crashes in heavily fed ponds, and why a filter that was working fine suddenly stops.
- Oxygen. The figure shown is the most dissolved oxygen the water can hold at that temperature. Warm water holds less, and nitrification alone burns about 4.2 g of O₂ per gram of ammonia on top of what your fish are using.
- Media figures are published typical values for each class of media. Real products vary — if your manufacturer lists a surface area, trust theirs over ours. Rates assume a healthy, fully cycled, well-oxygenated filter.
