The allometric growth was studied in cultured mangrove oysters Crassostrea rhizophorae, during about 5 months, under different wash cleaning management treatments (each 7 or 14 days) and densities (1,000 and 2,000 oysters/lanternet) commonly used by producer fishermen in southern Brazil, starting with 9 mm animals. In all treatments the oysters grew fast, going to more than 50 mm. The highest stock density and 14 days wash cleaning treatment had yielded the best growth on shell height. However, when we focus the analysis of volume, the best treatment was the 7 day wash cleaning management and lowest stock density. These results clearly demonstrate the allometric growth rate in oysters and the importance of using biometric parameters other than height to analyse the growth results in oysters where there are a strong relationship between shell growth and shape definition, stock density and culture management.