The colour of adult grass carp is dark gray on the dorsal surface with lighter sides (white to yellow) that have a slightly golden shine. Fins are clear to gray-brown (Page and Burr 1991, Opuszynski and Shireman 1995).

This species generally attain weights of 30-50 kg (Chilton and Muoneke 1992) and can reach lengths greater than 1 m (Fraser 1978, Pauley 1978, Page and Burr 1991, Nico and Fuller 2001).

As with most species, growth in grass carp is a function of age, size and abiotic factors such as density, nutrition, temperature and oxygen (Chilton and Muoneke 1992). The most rapid length increases seem to take place in age 0-4 fishes, while weight increases are especially pronounced for age 4-6 fishes (Chilton and Muoneke 1992). Shireman and Smith (1983) presented mean length for each year class for grass carp found in the Amur River basin (Figure 10).

Cultured grass carp may reach up to 1 kg in the first year and grow approximately 2-3 kg/yr in temperate areas and 4.5 kg/yr in tropical areas (Shireman and Smith 1983). A study by Shelton et al. (1981) of grass carp growth at different stocking densities indicate that the growth of age 0 fishes was strongly affected by density. After one year, average size decreased with increasing density, with maximum weights attained in ponds with the lowest density (Shelton et al. 1981). Grass carp require cellulose and protein in their diet, with protein being especially important for optimal growth in young fishes (40-120 g) (Chilton and Muoneke 1992).