Tilapia zillii were fed lettuce at water temperatures ranging from 20 to 34°C to determine the impact of temperature on the feeding rate and growth and to determine the optimum temperature for each. The optimum temperature for feeding is between 28.8 and 31.4°C, when the feeding rate averaged 171% of the fish's body weight of lettuce in 24 h. The fastest growth rate was at 31.4°C, at which the fish averaged an increase of 3.42% of their body weight in 24 h. T. zillii should be valuable for aquatic weed control wherever water temperatures exceed 22°C for a substantial portion of the year.