author(s)
P Yuvarajan, S Felix, Cheryl Antony, A Gopalakannan, M Menaga and S Ezhilmathi

abstract
The present study was conducted to evaluate the Aerobic Microbial Floc Technology (AMFT) on water quality and growth performance of GIFT tilapia (Oreochromis niloticus) fry in outdoor lined nursery pond. The experiment consisted of treatment (AMF) and control (non-AMF) group in duplicate. Spent wash was utilized for floc development (Treatment) and to establish a carbon/nitrogen (C/N) ratio of 10:1. The stocking density was 50 numbers per m³ (average body weight of 0.2054 g per fish) in each 100 ton capacity of outdoor lined pond. Ammonia level in the AMF treated group was lower (0.004 mg l^-1 ± 0.00 to 0.011 mg l^-1 ± 0.001) than non - AMF due to the addition of suitable carbonaceous substrate as spent wash. Total suspended solids concentration continuously augmented in AMF group (139 mg l^-1 ± 1.0 to 590 ± 75) than non- AMF (10 ± 1 to 66 ± 8) throughout the culture period. Total weight gain, individual weight gain, average body weight and daily growth rate were higher (11937 g ± 560, 3.85 g ± 0.014, 4.09 g ± 0.019 and 0.128 g day^-1 ± 0.00) in AMF system than control. FCR (1.39 g ± 0.01) was found to be lower even after reducing 20% feeding rate in AMF system than control. Significant difference (p<0.05) was observed on 24^th day. From the present study it is evident that AMF can improve the quality of culture water and results in best growth of GIFT tilapia.