عنوان مقاله [English]
In this study, the effect of oral green skin of walnuts on the coloration of Oscar fish (Astronotus ocellatus) was studied. Sixty albino Oscar fish with an average weight of 5/01 ± 0/18 g and 54/84 ± 2/23 mm average length were divided in into three test experiments and one control and each with three repetitions. Twelve aquariums in the dimensions of 50 × 40 × 33 cm were used. The control was fed with a diet containing no food additives. The fish in treatment number one were fed with food containing %0.1 walnut hulls, the second treatment contained %0.2 walnut hulls in the fish diet and the third treatment was fed with food containing % 0.3 walnut hulls. The breeding period lasted eight weeks (56 days). Every 20 days biometrics (Biometry) were performed which included gravimetric analysis using a digital scale with 0.01g precision and a ruler with an accuracy of 0.1 cm for length analysis. Average water temperature in the aquarium during the study period was 28/07 ± 1/09 ° C. An average of 5/38 ± 0/15 milligrams per liter of dissolved oxygen, average pH of 8/03 ± 0/33 and an average TDS of 33/27 ± 1/32 mg was measured. At the end of the period of investigation, results showed that in terms of growth, the control with an average weight of 17/06 ± 1/21 grams and weight gain of 22/15 ± 1/08 grams had significantly (P<0/05) the highest growth rate compared with the other treatments. The third treatment with an average weight of 6/95 ± 0/56 grams and weight gain of 2/12 ± 0/64 grams showed the lowest growth rates. The control treatment also showed increased body weight and had the highest average of 337/01 ± 38/62 percent and was significantly different (P<0/05) from the other treatments. Treatment no. 3 with an average of 44/60 ± 15/48 percent had the lowest percentage of weight gain. Treatment no. 2 with an average of 95 percent have the highest rateof survival and was significantly different (P<0/05) from treatment no. 1, but was not significantly different (P≥0/05) compared to other treatments. Treatment no. 1 with an average survival of 55 percent had the lowest survival rate.The results showed that using the green skin of walnuts in the diet can reduce the growth factors in Oscar fish. However, 0.3 percent green skin of walnuts in the diet was most effective in slowing the fish growth rate.