Giant Marimo Ball - Live Aquaticmagic Aquarium Aquatic Plant for Fish Tank diameter around 2 inch Diameter 1.5 to 2 inches Excellent gift for your friend or loved ones to signify everlasting love.... The Japanese believe that Marimo will bring good luck. Hence, they grow it in a glass bottle with just some water & ceiling light. Water change is only required once every 2 weeks Marimo is a very popular plant in Japan. Currently protected by the authorities to prevent extinction. The growth rate of Marimo is about 5 mm per year. Hence a giant marimo is about 7 years old!. This plant does NOT cause algae problem. Propagate by dividing into smaller pieces, which become spherical over time. Negligible maintenance required.