To explore the purification effect of shellfish and algae coupling on intensive aquaculture tailwater, we analyzed the coupling effects of oyster (Crassostrea hongkongensis
) and microalgae (Spirulina platensis
) on tailwater treatment of biological flocs which are rich in nitrogen and phosphorus nutrients. A total of five groups were set up. The average mass of oysters added to the small (S), medium (M) and large (L) size groups was (50.99±7.01), (100.25±8.87) and (148.81±15.61) g, respectively. The negative control group (NC) was only added with spirulina, and the blank control group (BC) was not added with oysters and spirulina. The density of spirulina was about 8×105
and oyster biomass was 3 kg·m−3
. The survival rate and growth of oysters were recorded, and the cell density of spirulina in water was counted under a microscope. The concentrations of \rmNH_4^\text+
-P, TIN, TN, TP and TSS in water were detected. The results show that the survival rate of oysters in the experimental group followed a descending order of S>M>L. The highest rate of weight gain was observed in Group M. The highest density of spirulina was (1.30±0.25)×107
in Group NC. The highest TSS removal rate in Group M was 30.61%. The NC group had the highest TIN and \rmPO_4^3\text−
-P removal rates of 89.29% and 98.93%, respectively. Group M had the highest TN and TP removal rates of 38.91% and 55.10%, respectively. The results suggest that spirulina has a significant effect on purifying inorganic nitrogen and phosphorus. Oysters can feed on spirulina in water effectively. Coupling oysters of average mass of (100.25±8.87) g with spirulina has the best effect on removing TN, TP and TSS from aquaculture tail water.