Construction Of Aquaponic System And The Influence Of The Application Of Nano-Se Feed On It

With the increase of people’s demand for aquatic products and the increasing awareness of environmental protection,traditional aquaculture methods can no longer meet people’s needs for the quality and quantity of aquatic products.Compared with traditional aquaculture,recirculating aquaculture system has the advantages of high unit yield and can be combined with water treatment technology to convert toxic ammonia nitrogen and nitrite nitrogen into nitrate nitrogen which is non-toxic to fish.The RAS system has the advantage of recycling water resources.But it cannot fully recycle nutrients in the water.For example,the nitrate will remain in the system,or it will be converted into N₂O by biochemical reactions and released into the air,causing pollution to the atmosphere.And the excessive accumulation of nitrate in water will affect the growth,health and metabolism of fish.The aquaponic system is a new culturing system that combines a circulating aquaculture system with hydroponic technology.Its operating principle is that insoluble large particles of feces produced by fish metabolism are separated by physical filtration,and bacteria are attached to biochemical filter materials through nitration.The bacteria will convert ammonia nitrogen into nitrite and nitrate,which are then absorbed and used by plants.The purified water is returned to the fish pond,and the water in the system is completely recycled.When the system is stable,the fish,microorganisms and plants in the system form a harmonious and healthy symbiotic relationship.The development and promotion of the aquaponic system can improve the utilization of water resources,reduce the environmental pollution caused by aquaculture,and provide solutions for food safety issues.It is unclear what impact the growth of fish in the circulating water system and the aquaponic system has on the water quality of the system,and this study is based on this starting point.This study aims to explore 1)coupling hydroponic vegetable units in factory-circulating aquaculture systems and using UV lamps to treat the system,study the effects of different treatment methods on frame growth and water quality changes;2)to aquaponic system feeds with different nano-Se concentrations（0 mg/Kg,0.6 mg/Kg,1.2 mg/Kg and 2.4 mg/Kg）were added to investigate their effects on the growth of Koi and lettuce and the environment of aquaculture.The results of the study were as follows:In order to explore a green and environmentally friendly circulating water culture model and construct a fish and vegetable symbiosis system,this experiment designed an aquaponic system（Aquaponic group）,an aquaponic system with a UV lamp（Aquaponic UV lamp group）,and a recirculating aquaculture system（RAS group）.54 frame scale mirror carp（average initial weight was 253.78±33.30 g）were divided into three groups,each group had3 repetitions,each with 6 fishes,and was cultured in an indoor circulating water and fish-vegetative symbiosis system for 42 days.Explore the effects of three different treatments on the growth of（Cyprinus carpio var.specularis）,leaf lettuce（Lactuca sativa var.Ramosa）,and water quality.The results showed that RAS system coupled with hydroponic unit had no significant effect on the growth performance of the mirror carp（P>0.05）,but it affected the biological characteristics of the mirror carp,the relative gut length（RGL）in the Aquaponic group was significantly lower than that in the RAS group（P<0.05）.The crude protein and crude fat of whole fish body in the Aquaponic group was significantly higher than that in the RAS group（P<0.05）.The crude protein of fish liver in the Aquaponic group were significantly lower than those in the RAS group（P<0.05）.Using UV lamps in aquaponic system could significantly reduce the total number of bacteria in the water of Aquaponic group compared with Aquaponic UV lamp group（P<0.05）.In terms of water quality,RAS system coupled with hydroponic unit could significantly decrease the content of Ammonia nitrogen,nitrate nitrogen,total phosphorus and total nitrogen in the Aquaponic group compared with the RAS group（P<0.05）.The content of nitrate nitrogen,total phosphorus and total nitrogen in the Aquaponic UV lamp group were significantly higher than that in the Aquaponic group（P<0.05）.In summary,RAS system coupled with hydroponic unit could improve water quality,improve the body composition and reduce the number of bacteria by using UV lamps to disinfection the aquaponic system.In the second experiment,the experiment aquaponic system was update based one the performance of aquaponic system in the first experiment.Different nano-Se content feeds（0mg/Kg,0.6 mg/Kg,1.2 mg/Kg,and 2.4 mg/Kg）were used for the koi carp,and 108 koi carp（average body weight of 125.26±12.55 g）were randomly divided into four groups,each with3 repetitions,each with 9 fishes,and cultured in an indoor aquaponic system for 56 days.The results showed that:（1）the weight gain rate in 0.6 mg/kg and 1.2 mg/kg nano-Se group were significantly higher than those of the control group（P<0.05）,the feed conversion ratio of 1.2mg/kg nano-Se group were significantly lower than those of the control group（P<0.05）.（2）Carotenoids content in serum,liver and skin of Koi carp were significantly increased in the1.2 mg/kg nano-Se supplementation group（P<0.05）and the skin redness of the 2.4 mg/Kg nano-Se group was significantly higher than the control group（P<0.05）.（3）the MDA level of liver in koi carp in 1.2 mg/kg nano-Se group was significantly lower than that of the control group（P<0.05）.（4）Total serum protein content increased significantly in the 1.2mg/kg and 2.4 mg/kg nano-Se supplementation groups（P<0.05）,and serum globulin increased significantly in the 2.4 mg/kg nano-Se supplementation group（P<0.05）.（5）The production and morphological indexes of lettuce were not influenced by the dietary nano-Se supplementation（P>0.05）.（6）The level of nitrogenous nutrients in aquaponic system were significantly decreased in the 1.2 mg/kg and 2.4 mg/kg nano-Se supplementation group compared with other group（P<0.05）.In conclusion,in the aquaponic system,dietary nano-Se supplementation in Koi feed could improve the growth performance,body pigment deposition and health status of Koi carp and effectively improves the aquaculture environment.The optimal Se level in feed of koi carp is recommended as 1.41 mg/Kg under the present experimental condition.In summary,the study found that the combination of hydroponic vegetable units in the circulating aquaculture system can improve the water quality and fish composition of the system,and the application of selenium-containing feed to the aquaponic system can positively affect the growth,health,and ornamental quality of koi.It has no significant effect on the lettuce yield,and the optimal feed selenium level of koi can significantly reduce the level of nutrients and improve the water quality of the system.It is considered that the optimum selenium content of koi carp feed in the aquaponic system is 1.55-1.57 mg/kg under the conditions of this study.