Document Type : Research Paper
Authors
1
PhD Graduate, Department of Fisheries, Faculty of Natural Resources, University of Tehran, Karaj, Iran.
2
Professor, Department of Fisheries, Faculty of Natural Resources, University of Tehran, Karaj, Iran.
Abstract
With the development of aquaculture during last years, there is increasing need to intensive culture methods and using recirculating water without losing its quality. Using ozone as a potent oxidant agent would lead to convert TAN and nitrite to nitrate and decrease in water turbidity. Among different methods of ozone injection, the method of serial injection has lower qualitative fluctuation and toxic impacts compared to others. The present study was conducted based on a factorial experimental design with a control (without ozone injection) and three ozonation levels (100-120, 250-300, and 450-500 mV) three times per day, each time 3 hours after feeding with two levels of water exchange (2 and 6% of total water volume). Twenty fingerling of rainbow trout, O. mykiss, (17.2±2 g) were randomly distributed to experimental tanks. Measurement of the water quality parameters and biometry of fish were determined during study period. Serial injection of ozone was led to increase and decrease of nitrate and nitrite, respectively (P<0.05), both of them were less in 6% than 2% water make up. Although the highest ozone level reduced 17.6% TDS, but this change was not statistically significant (P>0.05), Also, ozone and its interaction with the water make up, did not have a significant effect on total ammonia and total phosphorus (P>0.05). On the other hand, water make up had significant effects on concentration of TDS (P<0.01), total ammonia and total phosphorus (P<0.05). While the effect of water make up and its interaction with ozone levels on nitrate and nitrite concentration was not significant (P>0.05). Ozone significantly affected on (FCR) decreasing, condition factor (CF) and specific growth rate (SGR) increasing (P<0.05); while water make up and its interactions with ozone levels did not have a significant effect on these issues (P>0.05). Based on the results, it can be said that using ozone in ORP level about 450-500 mV, improved water quality and ozonation along with an increase in make-up water level to 6% would lead to decrease in food conversion ratio and improve of condition factor and specific growth rate, and is a useful approach that can be used in super intensive and recirculated aquaculture systems.
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