eight-stamened waterwort

Eight-stamened waterwort is a cool-water foreground plant that forms a dense, moss-like carpet of tiny rounded leaves on thin creeping stems. It is one of the few carpeting plants that does well without tropical temperatures: Flowgrow gives an optimum of 16 to 26 °C, and it thrives in unheated or lightly heated tanks where standard foreground choices like Hemianthus callitrichoides struggle. The pH is 6.4 to 7, and carbonate hardness between 4 and 8 dKH — moderately soft to moderately hard water all work. Lighting should be medium to high; at lower light the plant grows upwards rather than spreading horizontally, losing the carpet effect. CO2 injection at 20–40 mg/l is needed for dense growth; without it the stems stretch and the coverage becomes patchy. Growth is medium, meaning a full carpet takes several weeks even under good conditions. Propagation is by cutting sections of the runners and replanting them a few centimetres apart — each node roots and sends out new side shoots. The difficulty is rated difficult on Flowgrow, largely because the temperature and CO2 requirements are narrower than those of warm-water foregrounds. Above 26 °C the plant goes into decline, so it is not suitable for tanks with tropical fish that need steady 27–28 °C.