Silver carp and bighead carp were studied in fish pens in Lake Taihu to see how their growth is affected by stocking density. The growth rates of both types of carp were higher with lower stocking density. Bighead carp grew faster than silver carp, but stocking density had a bigger impact on their growth. Silver carp had one peak growth period per year, while bighead carp had two peaks. Water temperature affected silver carp's growth, while bighead carp's growth was hindered by cyanobacterial blooms in summer. To reach commercial size in one year, the initial stocking density of fingerlings should be less than 12 g/m3 in Lake Taihu.