An aquaponic system comprising: a frame; an aquarium located at a lower portion of the frame and having an interior provided with a motor; a plurality of cultivating tanks arranged on the frame in layers from top to down, each layer of cultivation tanks having two opposite sides provided with an inlet tank and an outlet tank; and a strainer unit mounted on the frame; wherein: each of the inlet tanks is provided with a water inlet seat; the water inlet seat of the uppermost one of the inlet tanks is connected with a water inlet pipe; each of the outlet tanks is connected with a lower one of the inlet tanks; each of the outlet tanks is provided with a water outlet seat which is provided with a water outlet tube; the water outlet tube of each of the outlet tanks is connected with the water inlet seat of a lower one of the inlet tanks; the water outlet tube of the lowermost one of the outlet tanks is connected to the aquarium; the strainer unit includes: a water outlet port connected with the water inlet pipe; a water inlet port connected with a water feeding pipe which is connected with the motor of the aquarium; two hollow clamping plates (65, 66) located between the water outlet port and the water inlet port; a filtering sponge clamped between the two clamping plates; a fertilizer ferment chamber located under the water inlet port; and a drain pipe connected with the fertilizer ferment chamber; and the water inlet port is located at a position lower than that of the water outlet port, wherein the dirty water of the aquarium is extracted by the motor and delivered through the water feeding pipe into the strainer unit a frame; an aquarium located at a lower portion of the frame and having an interior provided with a motor; a plurality of cultivating tanks arranged on the frame in layers from top to down, each layer of cultivation tanks having two opposite sides provided with an inlet tank and an outlet tank; and a strainer unit mounted on the frame; wherein: each of the inlet tanks is provided with a water inlet seat; the water inlet seat of the uppermost one of the inlet tanks is connected with a water inlet pipe; each of the outlet tanks is connected with a lower one of the inlet tanks; each of the outlet tanks is provided with a water outlet seat which is provided with a water outlet tube; the water outlet tube of each of the outlet tanks is connected with the water inlet seat of a lower one of the inlet tanks; the water outlet tube of the lowermost one of the outlet tanks is connected to the aquarium; the strainer unit includes: a water outlet port connected with the water inlet pipe; a water inlet port connected with a water feeding pipe which is connected with the motor of the aquarium; two hollow clamping plates (65, 66) located between the water outlet port and the water inlet port; a filtering sponge clamped between the two clamping plates; a fertilizer ferment chamber located under the water inlet port; and a drain pipe connected with the fertilizer ferment chamber; and the water inlet port is located at a position lower than that of the water outlet port, wherein the dirty water of the aquarium is extracted by the motor and delivered through the water feeding pipe into the strainer unit each of the inlet tanks is provided with a water inlet seat; the water inlet seat of the uppermost one of the inlet tanks is connected with a water inlet pipe; each of the outlet tanks is connected with a lower one of the inlet tanks; each of the outlet tanks is provided with a water outlet seat which is provided with a water outlet tube; the water outlet tube of each of the outlet tanks is connected with the water inlet seat of a lower one of the inlet tanks; the water outlet tube of the lowermost one of the outlet tanks is connected to the aquarium; the strainer unit includes: a water outlet port connected with the water inlet pipe; a water inlet port connected with a water feeding pipe which is connected with the motor of the aquarium; two hollow clamping plates (65, 66) located between the water outlet port and the water inlet port; a filtering sponge clamped between the two clamping plates; a fertilizer ferment chamber located under the water inlet port; and a drain pipe connected with the fertilizer ferment chamber; and the water inlet port is located at a position lower than that of the water outlet port, wherein the dirty water of the aquarium is extracted by the motor and delivered through the water feeding pipe into the strainer unit a water outlet port connected with the water inlet pipe; a water inlet port connected with a water feeding pipe which is connected with the motor of the aquarium; two hollow clamping plates (65, 66) located between the water outlet port and the water inlet port; a filtering sponge clamped between the two clamping plates; a fertilizer ferment chamber located under the water inlet port; and a drain pipe connected with the fertilizer ferment chamber; and the water inlet port is located at a position lower than that of the water outlet port, wherein the dirty water of the aquarium is extracted by the motor and delivered through the water feeding pipe into the strainer unit