The water quality was similar between the pond and tanks (Table 2) suggesting that the
superior performance of fish in the cages was not caused primarily by better water quality
in the pond. Despite the poorer water quality in the tanks stocked at 100 and 200 fish/m3
(Fig. 2), all variables were well within the acceptable ranges for silver perch listed by
Rowland (1995e). Although there were relatively high concentrations of TAN in tanks,
particularly those stocked at 200 fish/m3 during February and March (Table 2), concentrations
of NH3-N remained below levels known to reduce growth (Rowland, 1995e;
Francis et al., 2000) because of the relatively low pH values (Fig. 2). The similarity
between the water quality in the pond and in the cage stocked at 200 fish/m3 suggests there
was adequate exchange of water in the cages.