An aquaponic system includes a frame (20), an aquarium (10) located at a lower portion of the frame, a plurality of cultivating tanks (30) arranged on the frame and having two opposite sides provided with inlet tanks (40) and outlet tanks (50), and a strainer unit (60) mounted on the frame. Each of the outlet tanks is connected with a lower one of the inlet tanks. The strainer unit includes a water outlet port (61) connected with the water inlet pipe, a water inlet port (63) connected with a water feeding pipe (64), two hollow clamping plates (65, 66) located between the water outlet port and the water inlet port, a filtering sponge (A) clamped between the clamping plates, a fertilizer ferment chamber (67) located under the water inlet port, and a drain pipe (68) connected with the fertilizer ferment chamber.
