Figs. 3–5 show oxygen concentration dynamics in culture tank,
influent planted trough and effluent planted trough, respectively.
At the beginning of the system operation, the oxygen difference
across the system components was insignificant because of the
low system loading (low fish biomass and therefore low feed loading).
At the end of the experiment, oxygen concentration in culture
tank, influent planted trough and effluent planted trough then
reached a value of 4.70 mg/L, 4.35 and 4.2 mg/L, respectively. The
decreased of oxygen concentration with increasing in culture day
due to the increase of fish biomass and accumulation of organic
matter in the system.