This study analyzed the effect of water quality, different diets, and water temperature regimes in the conditioning and maturation of the Pacific oyster Crassostrea gigas. A recirculating aquaculture system prototype was used in this experiment and 2 different trials were performed. During the first trial, the effects of 3 different diets using different preserved concentrates of microalgae held at 20°C were tested: D1 (fed with Tetraselmis 3600), D2 (fed with Isochrysis 1800), and D3 (fed with a 50:50 mix of Tetraselmis and Isochrysis). During the second trial, 3 different temperatures regimes—T1, 16–24°C; T2, 20°C; and T3, 24°C (fed with preserved concentrates of microalgae at a 50:50 Tetraselmis and Isochrysis food ratio)—were evaluated. For each one of these treatments, 43 organisms were used and every treatment was done in triplicate. Seven samplings were completed in 72 days. During each sampling period, 9 oysters from each treatment were collected, and a gonad sample was obtained for histology analysis to determine gonad development. The results obtained in this study indicate that the recirculation system prototype was able to keep optimum water-quality parameters, and the nitrogenous components stayed below toxic levels (<0.2 mg/L). For the first trial, D3 showed gonad maturation at day 72, which was significantly different from D1 and D2 (P > 0.05). In the second trial, no significant differences were detected in gonad development among the 3 temperature treatments. Even when D2, T1, and T3 showed no gonad maturation, a trend was detected. Thus, it can be concluded that the combination of diet and temperature allows the manipulation of the gonad development of C. gigas, and that recirculation systems are an efficient tool to maintain appropriate physical—chemical and environmental parameters.