Blyxa japonica from my experience does better with co2. It really appreciate strong light and will reward you with many baby plants. With strong light, dosing and established aquarium, very soon you will have about 30 new plants from one planted in the substrate after 2 months. It will grow as a big bunch, but once you take it out you will immediately notice that this plant is already spreading to many other plants. Plant each seperately and you will have very nice forground to midground plants. In my opinion it looks the best next to the seiryu stones.