The present study aims to assess inter-specific competition between Hydrilla verticillata and Ceratophyllum demersum. A competition experiment design has five treatment combinations to terminal shoots of C. demersum only, terminal shoots of H. verticillata only and three different treatment combinations of C. demersum and H. verticillata together. Our results showed parameters growth of C. demersum were decreased of which, total chlorophyll, protein, and biomass while Superoxide dismutase (SOD), and Catalase (CAT) enzymes increase were significantly (p<0.05) compare with control treatment. While H. verticillata were increased total chlorophyll, biomass, CAT and little increase in protein and SOD were significantly (p<0.05) compare with control treatment. Therefore, due to the competition, with the introduction of C. demersum, the performances growth of H. verticillata were increased. Based on our result, showed H. verticillata and C. demersum species were coexist, C. demersum will have a competitive advantage over H. verticillata. Therefore, this study suggests, H. verticillata could out-compete for C. demersum in many situations, that despite the similar ecology.
