Japanese Blyxa

Blyxa japonica is a stem plant that grows only in water, in the shallow ponds, swamps and slow-flowing, iron-rich woodland rivers of subtropical and tropical East and South-East Asia, and in rice paddies. It forms grasslike tufts with a very short stem and dense, narrow leaves, and the whole plant sways gently in the current. It became well known through Takashi Amano's Nature Aquarium layouts in the 1990s and is still used as a midground accent in that style. It is not especially difficult when light is adequate, roughly 0.5 to 1 watt per litre or more, with CO2 and regular fertiliser. Under good light the tufts stay compact and take on golden or reddish hues; with weak light they grow taller, greener and lanky. The plant builds a large root system and does best in a nutrient-rich substrate or with bottom fertiliser. High phosphate levels, around 1 to 2 mg/l, can push it to send up long stems with tiny white flowers. It does not spread by long runners; new shoots grow at the base and can be cut off and replanted, though the stems are buoyant and need weighing down for a while. Tropica lists its height at 10 to 20 cm and more.