Biofilter Total Ammonia Nitrogen (TAN) Production Calculator
Fish excrete total ammonia nitrogen (TAN) as they digest the protein in their feed, and the biofilter must nitrify that TAN every day. This calculator estimates daily TAN production from the amount of feed and its protein content, using the formula given in the Kentucky State University Aquaponics Production Manual (Hager, Bright, Dusci and Tidwell, 2021, KYSU-000086, p. 21), taken from Timmons and Ebeling (2013). It is meant for recirculating aquaculture and aquaponics growers sizing or checking a biofilter.
Calculator
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How to use the calculator
- Choose how to enter the feed: Daily feed, or From biomass.
- For Daily feed, enter the amount of feed given per day and pick g/day, kg/day or lb/day.
- For From biomass, enter the fish biomass in kg or lb and the feeding rate in percent of biomass per day. The daily feed is then biomass × feeding rate / 100, in the unit of the biomass per day.
- Enter the protein content of the feed in percent, as stated on the feed label.
- Press Calculate to see the TAN production in grams, kilograms and pounds per day, TAN as a percent of feed, and the formula with your numbers filled in.
Where the 0.092 comes from
The coefficient 0.092 combines four factors:
- 0.16 protein is 16 percent nitrogen
- 0.80 80 percent of the nitrogen is assimilated by the fish
- 0.80 80 percent of the assimilated nitrogen is excreted
- 0.90 90 percent of the excreted nitrogen is TAN and 10 percent is urea
Multiplied together, 0.16 × 0.80 × 0.80 × 0.90 = 0.09216. The formula uses 0.092 exactly as printed in the manual, and so does this calculator.
Note
The formula gives TAN from feed protein, so feeds with more protein deliver more TAN.
In the manual example, 2,000 g of 32 percent protein feed per day gives 58.9 g TAN per day, about 3 percent of the feed rate.
Feeding rates as percent of biomass per day come from feed charts for the species and fish size, for example Table 5 of the same manual for tilapia.
Source: Hager, J., Bright, L. A., Dusci, J. and Tidwell, J. (2021). Kentucky State University Aquaponics Production Manual, KYSU-000086, p. 21. Formula from Timmons and Ebeling (2013).
This calculator gives an estimate of TAN production only. Measure TAN in the water to know the actual level in your system.