. Materials and methods
Broodstock rearing
The experiment was located in the field research facility of the
Department of Aquaculture, Faculty of Fisheries and Marine Science,
Bogor Agricultural University, Indonesia. Male and female tilapia
broodstock were obtained from the Wanayasa Nila Nirwana Development
Center, the Department of Fisheries of West Java Province (BPBIAT
Wanayasa,West Java, Indonesia). The fish were acclimatized to the local
rearing conditions for two weeks before the start of the experiment.
During this period, female and male fish were kept separately in three
outdoor tanks (3 m × 2 m × 0.7 m) previously filled with 3000 L chlorinated
and aerated water at a density of 40 fish per tank for female
broodstock and 20 fish per tank for male broodstock.
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 De
Schryver et al. (2008).