Abstract: Alternanthera sessilis Var. Rubra is a colourful foliage plant which has a high demand in ornamental aquatic plant industry. This study investigated the best N: P: K ratio to obtain maximum growth performance of Alternanthera sessilis Var. Rubra in order to cater the demand by cost-effective application of fertilizer. As per the results obtained (p<0.05), plants treated with 2N: P: 2K fertilizer ratio show the highest growth performance in terms of shoot length, fresh weight of roots, total leaf area and number of leaves. The plants that were treated with 2N:2P: K fertilizer ratio showed the highest growth performance for the growth parameters of root length, fresh weight of shoots and number of new nodes. Most of the growth parameters that are important for ornamental aquatic plant industry such as shoot length, total leaf area and number of leaves were given by the 2N: P: 2K fertilizer ratio. Hence, 2N: P: 2K fertilizer ratio is the best for Alternanthera sessilis (Var. Rubra) to obtain optimum growth performance for ornamental aquatic plant industry.