Carotenoids of different types and concentrations in commercial formulated fish diets affect color and its development in the skin of the red oranda variety of goldfish

The skin color of an orange-red hue in the Red Oranda variety of goldfish Carassius auratus is identified as a desirable and essential sales factor by hobbyists and commercial producers. This study used six different commercial diets (Arkat, BioKyowa, Silver Cup, Southern States, VibraGro, and Zeigler Tropical) to demonstrate the highly variable effect commercial diets could have on the skin coloration, survival, and growth of juvenile Red Oranda goldfish. Diets were selected based on their popular use in the tropical fish industry, the manufacturers' guaranteed nutritional analysis, and advertised color-enhancing ability. Goldfish were raised for 20 weeks in well water or pond water. Goldfish exhibited the best orange-red skin coloration when fed the VibraGro, Silver Cup, and Zeigler Tropical diets. BioKyowa feed imparted greenish-yellow skin coloration, and fish exhibited significantly (P < 0.05) faster growth. The Arkat and Southern States feeds produced light olive to greenish-yellow skin coloration, and fish exhibited poor survival and growth. Skin color acquisition was faster in pond-water-reared fish than those reared in well water. The carotenoid content in the commercial diets was determined by spectrophotometry and high-performance liquid chromatography. Although the carotenoid types in the different diets were similar, their concentration levels varied widely.