Biofloc technology (BFT) improves skin pigmentation of goldfish (Carassius auratus)

This study evaluated the effect of biofloc technology (BFT) system and the astaxanthin supplementation on the productive performance and skin pigmentation of goldfish (Carassius auratus). The effects of two production systems (clear water and BFT) and two diets (with and without astaxanthin supplementation) were evaluated in a completely randomized 2 × 2 factorial design. A total of 120 goldfish juveniles (average weight 12.18 ± 0.27 g) were individually weighted and distributed into 24 glass aquariums (15 l of useful volume). Two isoproteic (40% of crude protein) and isoenergetic (4250 kcal of gross energy kg⁻¹) diets were formulated according to requirements established for goldfish. A control diet without carotenoid supplementation was compared with a diet supplemented with 80 mg kg⁻¹ of astaxanthin. After 56 days, fish growth and skin pigmentation parameters were evaluated. No interaction (system x diet) was observed for any of the evaluated variables. Production systems and astaxanthin dietary supplementation had no effects on weight gain (4.00 g), specific growth rate (0.51% day⁻¹), survival (98.33%) and apparent feed conversion (3.78) of fish. Redness (a) and yellowness (b) values were higher in the fish reared in BFT system (a 7.71, b 40.47) when compared to clear water (a 3.49, b 37.63), and in fish fed with the diet containing astaxanthin (a 6.46, b 40.72) in relation to control diet (a 4.74, b 37.38). Skin carotenoid concentration was also higher in fish produced in the BFT system (50.36 mg kg⁻¹) when compared to clear water (35.63 mg kg⁻¹) and fish fed with the astaxanthin diet (49.33 mg kg⁻¹) in relation to the diet with no supplementation (36.66 mg kg⁻¹). These results demonstrate that the BFT system is an effective and promising technology for goldfish (Carassius auratus) production. The BFT system promotes pigmentation, but this effect can be intensified with exogenous sources of carotenoids.