EFFECT OF STOCKING DENSITY ON TILAPIA PERFORMANCE AND WATER QUALITY DURING INTERMEDIATE GROWING PHASE UNDER BIOFLOC SYSTEM

The major constraint in the adoption of tilapia culture to marketable size is the longer duration of culture. Therefore, efforts are needed to reduce the culture duration by phasing out the culture period and it is important to develop intermediate growing phase for tilapia in order to use up the most space available, and improve management techniques. The objective of this study was conducted to determine the ideal stocking density for tilapia farming in biofloc system without water renewal under intermediate growing phase.

Nile tilapia with an average size of 35 g were reared for 84 days at densities of 20, 40 and 60 fish/m3 in a zero-exchange biofloc water system. Each group consisted of four tanks. Fish fed at a feeding rate of 2.5% body weight/day with 25% protein commercial pellets. During the culture period, starch was added into the BFT tanks to maintain carbon/nitrogen ration in water 10:1. Fish were fed six days a week. Data were analyzed as a one-way ANOVA using SPSS program. Means were separated using Duncan's multiple range test.

Total ammonia, nitrite, nitrate, and pH were within acceptable limits. The results indicated that the individual fish performance and feed utilization efficiency were inversely related to increasing stocking density. The net yield increased with increasing density levels. No significant differences in whole body  chemical composition (moisture. crude protein, crude fat, total carbohydrates, macro minerals and micro minerals) were recorded. The results obtained indicate that from economically point of view, stocking 60 fish/m3 is recommended for cultivating tilapia under intermediate growing phase.  This work was supported by Science & Technology Development Fund (STDF), Egypt under grant no 5671.