Not surprisingly the total bacterial number was low in RAS at start, but later increased to the same levels as in raw incoming water and FTS. Survival and yield from larval cultures are affected by a number of factors comprising the water quality. Bacterial blooms have been reported to cause problems in static larval cultures (Robert et al., 1998; Bergh and Strand, 2001; Torkildsen et al.,2005). However, no evidence has been presented to show that the bacteria are a primary cause for mortality and not a result of unfavorable culture environment (Andersen et al., 2011)