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Paller 13 Equation 12 can be used to approximate the biomass of fish that will be supported at different ammonia concentrations under 2.0 mg/1 in any submerged biofilter if an initial estimate of R is avail- able from a biofilter of the same type employing the same medium. In this respect, it differs from other models and design procedures (summarized in Wheaton 1977} that are appropriate for a relatively narrow range of conditions. Equation 12 predicts carrying capacity on the basis of the ammo- nia excretion rate per unit of fish biomass (Table 1). Because the ammonia excretion rate is a function of the feeding rate, it is some- times more convenient to work directly with the relationship be- tween feeding rate and ammonia production rate. In such cases, A TABLE ] . Totaiammonla-nitrogen production rates of several types of fish. Feeding rate Ammonia-N Ammonia-N (percent body production rate production Taxa Temp, (°C) weight/day) Img/kg fish/min) 1g/kg food] Cyprinus carpio (100-600 g)a Ictalurus punctatus Salmo (15 cm) Oncorhynchus nerka (average - 29 g) Norone saxltilus 20 1.0 0.]232 18,2b - c 0.0 0.05]7 - d - 0.7 0.1100 22. 6d - 0.7 0.1033 21. 3d - 1.4 0.2050 21. 1d 4 1.0 0.1517 22. Oe 7 1.0 0.1667 24. Oe 10 1.0 O.1B67 27. Oe 13 1.0 0.2017 29. Oe 16 1.0 0.2150 31. Oe 16 2.0 0.4300 31. Oe 15 0.0 0.1367 - t 15 >0.0 0.1367-0.5833 - f _ g _ 9 - 27. Oh aSize in parentheses where known eSpeece 1]973) bPaller (1987) (Brett and gala 11975) cvalue unknown gvariable dWalker and Simco (1977) hLewis ei al. 11981)