Green macroalgae Ulva lactuca and Black soldier fly (Hermetia illucens, L.) larvae in the Diet of Nile tilapia (Oreochromis niloticus): Effect on the growth performance and feed utilization

This study was conducted to assess the effect of the green macroalgae Ulva lactuca and black soldier fly larvae (Hermetia illucens, L.) on the growth performance and feed utilization of Nile tilapia (Oreochromis niloticus). Four experimental diets containing different proportions of Ulva lactuca and black soldier fly larvae were developed to meet the nutritional requirements of Nile tilapia (approx. 21.7 MJ/kg gross energy). Diets were tested in triplicate. The fish were fed three times a day at 9:00 am, 1:00 pm and 5:00 pm for 45 days.

A total of 360 Tilapia juveniles with an average weight of 12.72± 0.3g and an average length of 8.86 ± 0.5cm were stocked in twelve rectangular tanks fed by a recirculating aquaculture system.  Each tank (0.8 meter cube) had a water volume of 300 L/500 and was stocked with 30 fish, giving a density of around 0.1 g/L. During the acclimatization period (15 days), Tilapia were fed to satiation with a commercial feed (2mm, Protein 28%, Mineral matter 20%, Fat & oil 5%, Moisture 12%). During the experimental period (2 weeks), the physico-chemical parameters of the water were regularly checked using the Hanna Oximeter, the HI-gghhh Aquaculture Photometer. Temperature (19.5 ± 0.3°C), dissolved oxygen (5.77 ± 0.6 mg/l), pH (7.2 ± 0.3), Amonia NH3 0.28 mg/l, nitrite NO2 <0.01mg/l. Phosphate (0.44 ± 0.01mg/l) and Alkalinity CaCO3((184 ± 0.3mg/l). In order to maintain pH at 7, a permanent supply of fresh water was provided in the ratio (2:1). The effect of the four experimental diets on the growth performance and feed utilization of Nile tilapia will be measured on fish performance, including weight gain, specific growth rate, feed conversion index and other parameters such as K coefficient. After 5 weeks, the fish had an average weight gain of 6.19 ± 0.2 g and an average length gain of 1 ± 0.1 cm.

 At the end of the feeding trial, we found that feed 1 with the following formula: 50% black soldier fly larvae meal + 25% Ulva lactuca mix + 25% fish meal, tested in tanks 1, 2 and 3, performed better than the other feeds.

Keywords: Ulva lactuca, Hermetia illucens, Oreochromis niloticus, Diet, growth, feed utilization