Based on information gained from a pilot model, two identical revolving plate filters were designed to be evaluated for use in a recirculated fish production system. Each unit consisted of a fiberglass tank containing 787 liters of water; a biofilter having 60 plates, each 51 cm in diameter, rotated at 6 rpm; and a settling tank. The total water volume in each unit was 1,132 liters. Water was continuously passed through the filter at a rate of 9 liters/min, and fresh water was added to the fish tank at a rate of 0.45 to 0.72 liters/min. In a trial designed to determine loading rate, it was found that each of the units could support at least 45 g of channel catfish (Ictalurus punctatus) per liter of the total volume of water in the system, and approximately 2 kg/m2of surface area of the filter. By extrapolation, carrying capacity on the basis of fresh-water flush was 71 to 113 kg/liter/min. In a growth trial, the fish in both units grew at an acceptable rate for the temperature at which they were held. In both trials, ammonia, nitrite nitrogen, nitrate nitrogen, methyl orange alkalinity, pH, and oxygen remained at desirable levels. It appears that this type of filter has some features that are particularly attractive for use in recirculated fish production units or holding facilities.