Comparison of the effectiveness of the combined diet of concentrated food with gammarus, bloodworm and mixed (gammarus and bloodworm) on growth performance, survival rate, and skin color of white Oscar fish (Astronotus ocellatus)

Abstract

Introduction: The aquarium is one of the most popular human entertainments around the world. Because of shape, color, and behavior, ornamental fish are known as living jewels. The market value of ornamental fish increases with the improvement of skin color. Gammarus is a suitable live food for aquatic animals due to its high amounts of beta-carotene and antioxidants, as well as its ability to retain its nutritional properties in the forms of biomass and dry. Chironomid has a very high nutritional value, so its protein content is 55.7% of dry weight, and it is rich in amino acids. This research was conducted to investigate the effect of the combined diet of concentrated food with gammarus, bloodworm, and mixed (gammarus and bloodworm) on the growth, and skin color of white Oscar fish (Astronotus ocellatus) during 45 days. Materials & Methods: A total number of 84 Oscar fingerlings with an average weight of 7.37±0.09g were randomly distributed in 12 aquariums at a density of 7 fish in each aquarium. After the adaptation of the fish to the new rearing conditions, Oscar fish were fed with four diets including diet: 1- Biomar commercial food; diet 2- 50% Biomar commercial food+50% gammarus; diet 3- 50% Biomar commercial food+50% bloodworm and diet 4- 50% commercial food Biomar+25% gammarus+25% bloodworm (mixed) in triplicate groups. At the end of the experiment, growth indices and skin coloration were measured. Results: The fish fed mixed diet showed significantly higher final weight, final length, percentage of body weight, average daily growth, and specific growth rate compared to other treatments (p<0.05). Also, the lowest food conversion ratio was determined in the mixed diet, and the survival rate was 100% in fish fed the mixed diet and bloodworm, which showed a significant difference with the gammarus treatment (p<0.05). The diets containing gammarus, blood worm, and the mixed diet recorded the highest (p<0.05) intensity of red color in the skin compared to Biomar diet, respectively. The highest amount of red color belonged to gammarus. Conclusion: According to the obtained results, the animal sources of carotenoid can affect the growth and skin color of white Oscar fish.