Water temperature was elevated and maintained in two of three fish production systems which incorporated biofiltration and hydroponics. Channel catfish (Ictalurus punctatus) were stocked in indoor fish tanks and fed to satiation once daily. Tomatoes (Lycopersicon esculentum) were planted in outdoor hydroponic tanks. The study was conducted during the 1979 growing season. Afternoon water temperature averaged 25°C in the control system and 28°C in both experimental systems. The temperature in the control unit varied with the ambient diel cycle, whereas the temperature in the two experimental units remained constant. The mechanics of the system were satisfactory and the plants showed no adverse effects associated with the heated water. The total fruit yield (in kilograms per plant) was similar in all systems: control, 8.9; experimental A, 9.1; and experimental B, 9.1. Growth of the yearling fish was enhanced by the constant elevated temperature. The respective average rates of growth from 15 May to 22 June in the control system and experimental systems A and B were 0.96, 1.47, and 1.06 g/day per fish.