Study of the effects of different monosex Nile tilapia (Oreochromis niloticus) fingerlings densitieson Lettuce (Lactuca sativa) and water quality in a low-techrecirculation aquaponic system

Abstract

The sustainable food initiatives and awareness amongst development interest has increased rapidly the technology of aquaponics in recent years due to widespread interest in local agencies that aquaponics may allow for the production of both vegetables and fish in water-deficient or soil-deficient zones. The present study aimed to compare rearing of three different fish (Oreochromis niloticus) fingerlings densities on the growth of lettuce (Lactuca sativa var. capitata) and water quality in a shallow water low-tech recirculation aquaponic system. The experimental aquaria were designed in 12 longitudinal aquaria of equal volum of 105L.3The treatments (Aquaponic vs Hydroponic) in this study were set-up for 56 days under 4treatments with three replications. T1, control (lettuce plant only using Hoagland solution), T2, T3, and T4 where stocking density of tilapia were 150(15 fish/ aquar.), 175(17 fish/ aquar.) and 200(20 fish/ aquar.) fish/m3 with Lettuce plants, respectively. Fish was fed up to satiation twice a day with commercially available floating pellet with 30% protein level. The wastewater from the fish aquarium was irrigated to the vegetable bed by a 40 watt submersible water pump. During the experimental period different water quality parameters were monitored regularly. Growth and yield of Lettuce were measured by means of fresh weight, dry weight (g), leaf area (cm2), and Chlorophyll (SPAD). The range of water temperature was 27 to 29o C (av. 28 o C), dissolve oxygen 6.8 to 7.4 mg/l (av. 7.1 mg/l), pH 7.10 to 7.4(av. 7.25), total ammonia (mg/l) 0.10 to 12.0 mg/l (av. 0.11 mg/l), nitrite (mg/l) 0.003 to0.005 (av. 0.004 mg/l) and nitrate (mg/l) 140 to 180 (average 160 mg/l). At the end of the experiment, the study suggests that stocking density of 20 fish/aquarium for tilapia, i.e.200 fish/m3 with Lettuce plants, is suitable for production of both plant and fish in a recirculating aquaponic system because of higher nutrient availability in this aquaponic trough.