As a start of the experiment, 2 concrete rectangular outdoor tanks
with a dimension of 3 m × 2 m × 0.7 m and a working water volume
of 3 m3 were stocked with 25 brood fish at a female:male ratio of
4:1. The two tanks were maintained in a different way, one without
organic C addition (control) and one with organic C addition (biofloc
technology or BFT). Aeration was provided using an air blower. Commercial
floating feed (Sinta Feed, Indonesia) was provided twice daily
in each tank at a feeding level of 2.5%/day on fish biomass. Molasses
(53% C) was used as the organic C source in the BFT treatment and
was added daily at an estimated C/N ratio of 10 as described in