Dietary <i>Rosa rubiginosa</i> petal supplementation improves growth performance, skin pigmentation, immunity, antioxidant capacity, and intestinal microbiota in <i>Carassius auratus</i>

Natural additives are gaining attention in ornamental fish aquaculture due to their potential to enhance health and colouration. Rose petals (RP) contain diverse bioactive compounds, yet their functional effects in goldfish (Carassius auratus) are not well understood. This study aimed to evaluate the effects of dietary RP powder on growth, pigmentation, antioxidant defense, immune gene expression, and gut microbiota in goldfish. A total of 300 fish (6.75–6.90 g/fish) were fed diets containing 0, 5, 10, 20, or 40 g/kg RP for eight weeks. Fish fed RP diets, particularly at 40 g/kg, showed significantly greater final weight and weight gain than the control (p < 0.05). Skin redness increased in RP-20 and RP-40 groups, while yellowness was highest in RP-40 (p < 0.05). Serum antioxidant indices improved with increasing RP levels, evidenced by elevated ABTS and SOD activities and reduced MDA levels (p < 0.05). Intestinal expression of antioxidant (hsp70, cyp1a), growth (igf, tgf), and immune (lyz, tnfα) genes was upregulated in RP-20–RP-40 (p < 0.05). RP supplementation significantly shifted gut microbiota composition (β-diversity, p = 0.017), with higher Staphylococcus and lower Alloprevotella abundances, but did not alter α-diversity. Overall, RP inclusion enhanced growth, colouration, antioxidant status, and immune responses in goldfish, demonstrating its potential as a sustainable functional additive for ornamental fish diets.