While under Harris family ownership, Kawainui was used for rice cultivation by Chinese farmers; the vast majority of the fishpond was being used for this purpose by 1900, but it was still publicly known as a fishpond. In 1917, Nannie Harris sold her land to Harold Kainalu Long Castle. In the early 1920s, water from Kawainui was drained and used for sugarcane in Waimānalo. Rice cultivation began to decline, and most of the former rice paddies were used for ranching by Harold Castle, who introduced large numbers of invasive plants in order to feed his cattle.
