In-situ environmental amelioration potential of biofloc media mediated through the removal of nitrogenous metabolites, reduction of pathogenic Vibrio with concurrent increase in Bacillus community and reduction of feed was studied in white Litopenaeus vannamei culture. Three treatments viz. biofloc without neem+ commercial feed (B), biofloc with neem +commercial feed (NB), only commercial feed without biofloc (F)and, one control (C) withno biofloc and no feed in triplicate was employed with a stocking density of 60 PL-20 m3 in outdoor earthen ponds (1000 m3). Two biofloc media (C: N = 15-10:1) with and without neem leave extract were applied with reduction of supplementary feed from 50% to100%. Final body weight in neem based biofloc media was higher than the others. with high survival (87%). Superiority of biofloc system over the feed based system was established as live weight gain was higher by 28.48-137 % with reduced FCR (7.60% - 8.18%) in the former. Ffeed cost was reduced both in B (8.1 %) and NB (8.77%) compared to feed based culture system (F). Biofloc system supported cumulative increase of Bacillus population with concomitant reduction of luminous Vibrio population.