In the excretion tests with feeding, fish were fed twice a day
at 10:30 h and 16:30 h at 1% of the total reared biomass, divided
in two rations: 50% in the morning and 50% in the afternoon.
Visual inspection was used to verify that the animals ate the entire
ration delivered at each feeding period. Water samples were taken
in triplicate simultaneously at the affluent and effluent sections
points of the tanks and were immediately analyzed for TAN (salicylate
method) via colorimetric measurement with HachTM reagents
using a spectrophotometer (Hach® spectrophotometer, DR-2800
model). Both RAS1 and RAS2 also included tanks operated without
fish (controls) and installed on the same water line as their respective
experimental groups in order to determine whether there was
any TAN consumption/production occurring in the culture tanks
apart from the TAN excreted by the animals