en Ecology Ecology پژوهشي Orginal research papers 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 semi-industrial 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 &micro;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&nbsp; 4.96 mg L^-1<span dir="RTL">.</span> Furthermore, pH and EC were 7.22 and 1466 &micro;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 18^th 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.<span dir="RTL"></span> Nanoparticle reactor, Wastewater, Fish farm, Iron oxide nanoparticles 1319 1328 http://jifro.ir/browse.php?a_code=A-10-2184-1&slc_lang=en&sid=1 M. Askari Hesni mahesni@gmail.com 100319475328460034063 100319475328460034063 Yes Department of Biology, Faculty of Sciences, Shahid Bahonar University of Kerman, Kerman, Ian. S.A. Hedayati hedayati@gau.ac.ir 100319475328460034064 100319475328460034064 No Department of Fisheries and Aquatic Ecology, Faculty of Fisheries and Environmental Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Golestan, Iran. A. Qadermarzi amirqmaleki@gmail.com 100319475328460034065 100319475328460034065 No Department of Fisheries and Aquatic Ecology, Faculty of Fisheries and Environmental Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Golestan, Iran. M. Pouladi mojtabafishery1987@gmail.com 100319475328460034066 100319475328460034066 No Department of Fisheries and Aquatic Ecology, Faculty of Fisheries and Environmental Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Golestan, Iran. Z. Zangi Abadi majidask@gmail.com 100319475328460034067 100319475328460034067 No Research and Technology Institute of Plant Production (RTIPP), Shahid Bahonar University of Kerman, Kerman, Iran. N. Naghshbandi mehrdadi2009@gmail.com 100319475328460034068 100319475328460034068 No Department of Biology, Faculty of Sciences, Payame Noor University, Oshnavieh, Iran.