One hundred and twenty red fantail male guppies (Poecilia reticulata) with an average weight of 0.64 ± 0.07 g were fed ad libitum a control diet without any herbals (0), 20 g/kg garlic, 20 g/kg red onion, and 20 g/kg sweet red pepper powders in 12 circular tanks for 60 d. The herbal treatments had significantly higher weight gain (94.70 ± 0.89 to 96.26 ± 0.90%), protein (3.58 ± 0.05 to 3.72 ± 0.06 mg/ml), ACH50 (1.41 ± 0.00 to 1.56 ± 0.00 U/ml), Ig (0.16 ± 0.00 to 0.32 ± 0.02 mg/ml), lysozyme activity (60.33 ± 0.88 to 68.00 ± 1.15 U/ml), carotenoids in lateral skin body (5.75 ± 0.025 to 8.26 ± 0.003 µg/g), and caudal fin (6.49 ± 0.003 to 10.10 ± 0.005 µg/g) than the control. Therefore, dietary garlic and sweet red pepper can be used for immunity and coloration in red fantail male guppies. [ABSTRACT FROM AUTHOR]