Aquatic vascular plants have evolved from different terrestrial ancestors, that independently returned to good in - or upon - the surfaces of water bodies. But many aquarists would still be astonished to learn there is a grass, that you can grow in your aquarium. Hygrororyza aristata belongs to a subclade of the grasses that has an affinity with freshwaters, and includes the domesticated rice that is grown in the famous, wet paddyfields of Asia and elsewhere. Within this group, Hygrorhiza is a closer sister of Zizania, than of the true rices, in the genus Oryza. But it is also unique among grasses for its floating habit. Although some people call this plant the floating bamboo, it is not a bamboo - although of course, the bamboos, too, are grasses, but they are more related to wheat, oats, and barley.
Hygrorhiza is naturally distributed from South Asia to the southern Chinese mainland and Taiwan, and it is a wild plant, although it is often found in manmade environments, such as thd paddies where it's cousin is cultivated by man. Human activities have since distributed this plant outside of its natural range. Known for good reason as the Asian water grass, Hygrorhiza is a plant of still waters with a seasonally variable growth habit in the wild, because it may be found both rooted, and floating, for its spongy stems are buoyant. In the months when the water levels drop, Hygrorhiza roots itself into the ground.
H. aristata has a wide tolerance of temperatures and water chemistry, because these values may fluctuate in its natural environment. For example a beel might be as warm as 30 degrees centigrade in the hot season, but as cool as 13 degrees in the winter; whereas the water in these ecosystems may be slightly acidic of quite alkaline. When it is the wet season, Hygrororyza floats on the water surface, profusely producing feathery roots that access the water column. Therefore Hygrorhiza is quite suitable for use as a floating plant in freshwater aquariums. Although people sometimes feel daunted or confused by this oddity, it really is unproblematic in just about any freshwater aquarium with at least medium lighting; this plant benefits from aquatic fertilizer.
