This study was conducted to elucidate mixing characteristics of the media to dertermine hydraulic model parameters of the three phase fluidized bed for the water quality management of aquaculture. The volume and H/D ratio of the reactor were 1.76 Liter and 10.9, respectively. The experimental results showed that variance $(sigma^2)$ and dispersion number $(D/{mu}L)$ were above 0.47 and $0.35~infty$, respectively. Therefore, the condition of the reactor was almost ideal complete mixing. The dependence of the overall oxygen-transfer coefficient $(K_{La})$ on each experimental variables through a multple linear regression was given by the following equation ; $$K_{La};=;44.9(D_i/D_c)^{-0.4611};A_f^{0.8622};C_m^{-0.0746};d_p^{-0.4302}$$