Effects of feeding frequency and photoperiod on water quality and crop production in a tilapia-water spinach raft aquaponics system

A factorial arrangement of 6 treatments, 2 photoperiods for water spinach Ipomoea aquatica (12-h or 24-h light per day) X 3 feeding frequencies for red tilapia Oreochromis sp. (an equal daily ration evenly fed 6, 4 or 2 times at 4-h, 6-h or 12-h interval, respectively) were assigned to 12 tanks. Each tank was an aquaponics system containing fish and raft-supporting plant. Water loss in 4 weeks was 3.3%, due to leaf transpiration mainly and evaporation. Water quality remained safe and stable. No fish died. Overall average weight gain was 43.9% for fish and 169.0% for plant. 24-h light resulted in 2.4% higher fish growth, 12% higher plant growth and lower accumulation of all nitrogen and phosphate species in water than 12-h light. Increased feeding frequency favored stable and good water quality and fastened fish growth and plant growth by as much as 4.9% and 11%, respectively.