Antifungal effects of formalin was evaluated on hatch rate of common carp (Cyprinus Carpio) eggs under water quality variables including dissolved oxygen (7.3+0.8 mg/L), water temperature (19.8+1 .8C°), PH(8. l±0. 1), total hardness (286mg/L) and inletwater (1.8+1.06 L/min). Groups of eggs were treated with formalin at concentrations of 250, 500, 1000, 1500 and 2000 mL/L for 30 minutes about 40 hours after incubation period. The obtained results showed that there was significantly difference between the hatch rates of all treated eggs groups and control one (P<0.05). Also there was no significant difference between the hatch rates of groups treated with formalin at concentrations of 200 and 500 1.tL/L and groups treated at concentrations of 1000 and l500 mL/L (P>0.05). 1-lowever, there was significantly differences between other treated groups (P<0.05). Maximum hatch rate of %93.7 was obtained in group treated with 2000 1.tLIL of formalin, while minimum hatch rate of %59.73 was found in fish treated with both 250 and 500 IIL/L. Therefore, in aquaculture practice it is recommended to use formalin at a concentration of 2000 1.tL/L for 30 minutes about 30-40 hours after eggs incubation in this area.
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