en aquaculture aquaculture پژوهشي Orginal research papers <span style="font-size:11pt"><span style="line-height:120%"><span style="tab-stops:dotted 5.95in"><span style="font-family:Calibri,sans-serif"><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times=""><span style="color:black">This study was conducted in order to compare the </span></span></span></span><span lang="TR" style="font-size:12.0pt"><span style="line-height:120%"><span new="" roman="" style="font-family:" times=""><span style="color:black">hornwort aquatic plant (<i>Ceratophyllum demersum</i>) with an artificial filter for purification in a recirculating aquaculture system (RAS). At first, the fluctuation of nitrogen components of the water reuse system equipped with artificial filtration was evaluated. Experiments were performed during three months. The hornwort aquatic plant was collected from Siadarvishan River and brought to the breeding and rearing system (JANAT Agriculture high school-Rasht). Subsequently, the plants were kept in river water for one month for adaptation. Initially, the plant wet biomass was weighted. For this purpose, 600 fishe specimens from the Cichlidae family (Oscar, Anjel, Burli and Zebra) provided from a local market were distributed between 12 aquarium tanks (160-liter capacity) in triplicate groups. Nitrogen component of water, such as ammonia (NH₃), nitrite (NO₂^-) and nitrate (No₃) were measured. Growth parameters and survival rate of fishe specimens at the end of the trial were evaluated. The results of this experiment indicated that nitrogen component when using hornwort aquatic plant as a biofilter not show better performance than the artificial filter treatment. The growth parameters performances when using the aquatic plant as biofilter in comparison with artificial filter declined.</span></span></span></span></span></span></span></span> Recirculating aquaculture system, Cichlid, Ceratophyllum demersum, Biofilter 422 430 http://jifro.ir/browse.php?a_code=A-10-3191-1&slc_lang=en&sid=1 E. Asadi Sharif ehsanasadisharif@gmail.com 100319475328460045541 100319475328460045541 Yes Faculty of Natural Resources, University of Guilan, Sowmeh Sara, Iran, P.O.BOX: 1144. J. Imanpore Namin 100319475328460045542 100319475328460045542 No Faculty of Natural Resources, University of Guilan, Sowmeh Sara, Iran, P.O.BOX: 1144. Z. Ramezanpoure 100319475328460045543 100319475328460045543 No Department of Ecology, Interntional Stugeon Research Institute, Agricultural Research, Education and Extension Organization, Rasht, Iran