This study was conducted to remove contaminations from Fish farms effluents using iron oxide nanoparticles in a laboratory system. For this purpose, a 5-liter semiindustrial reactor has designed with a mixer blade, a porous plate, and a compressor. The results showed that the levels of nitrate, nitrite, phosphate, ammonium, TDS, TSS, and BOD were 2. 78, 3. 27, 0. 43, 7. 46, 2. 25, 3. 38 and 5. 34 mg L-1 at the entrance to the reactor, respectively. Also, pH and EC were 6. 36 and 1362 μ mho cm-1. At the reactor outlet, the levels of nitrate, nitrite, phosphate, ammonium, TDS, TSS and BOD were 1. 84, 2. 09, 0. 27, 3. 05, 1. 61, 1. 78 and 4. 96 mg L-1. Furthermore, pH and EC were 7. 22 and 1466 μ mho cm-1. Also, this study has been showed that the system efficiency from the beginning up to 6 hours has been increased, but it has been reduced at the 18th hour, which has been caused by the sequestration and the formation of an oxide layer on nanoparticles. Therefore, it can be concluded that iron nanoparticles in the reactor fluid space have the potential to reduce the discharge burden of the effluent from Fish farms.