An attempt has been made to assess the efficiency of Hibiscus petals and Spirulina added diets on variation in biochemical constituents and total carotenoids in skin and muscle tissue of gold fish Carassius auratus. For this isonitrous (37% protein) diets (D1 and D2) supplemented with Hibiscus petals (5%) and Spirulina (5%) were prepared individually and offered to the candidate fish in 5% body weight at ad libitum for a period of 40 days. Simultaneously a control diet (C) with 37% protein but devoid of neither Hibiscus petals nor Spirulina was also prepared and used for experimentation. The results indicated that in the skin and muscle tissues of candidate fish, the protein, carbohydrate and lipid contents were found to vary between diets and also during various time intervals of experimental period. In Hibiscus petals supplemented diet fed fishes, the skin and muscle protein content varied from 4.65 ± 0.110 to 6.46 ± 0.240 mg/100 mg wet tissue and from 7.41 ± 0.280 to 9.26 ± 0.610 mg/100 mg wet tissue, respectively. Likewise, in Spirulina fed fishes, the skin and muscle protein content varied from 4.65 ± 0.160 to 6.98 ± 0.380 mg/100 mg wet tissue and from 7.41 ± 0.280 to 9.92 ± 0.520 mg/100 mg wet tissue, respectively. But in control diet fed fishes, the skin and muscle protein content recorded was less when compared to experimental diets (D1 and D2) fed groups and here the values registered were: 4.65 ± 0.146 to 5.48 ± 0.168 mg/100 mg wet tissues and 7.41 ± 0.280 to 8.14 ± 0.320 mg/100 mg wet tissues. More or less, a similar trend was noticed for the skin and muscle carbohydrate and lipid contents of experimental fishes, which received D1 and D2 diets. The dietary addition of Hibiscus petals and Spirulina has also influenced the total carotenoid content in the skin and muscle tissues of C. auratus. Two-way analysis of variance indicated that both the feed supplement and experimental duration significantly (P < 0.001 to < 0.05) influenced the total carotenoid content of skin and muscle tissue of C. auratus.