Hemianthus glomeratus has been in the hobby a long time and is known by many names. Shops often call it 'Baby tears' or 'Pearl weed'. Botanically, it was named Hemianthus micranthemoides "HM" and Micranthemum micranthemoides "MM" before but it was discovered in recent years to be neither of those plants. Its true name is Hemianthus glomeratus. However, other than a handful of botanists and enthusiasts, it seems rare to find anyone using the actual correct name. Commercial brands still continue to use "Hemianthus micranthemoides" on their labels most of the time.
Hemianthus glomeratus is a green stem plant with thin green leaves and thin green stems. The leaves of H. glomeratus are opposite (with 2 leaves per stem node) but it often also grows in whorls of 3 to 4 leaves. Its small size coupled with its ease of growing makes it a top choice for aquascapers as it can be flexibly placed any where in an aquascape. It can be a dense background bush or a small foreground plant depending on how short you trim it.
Pearlweed is used on both the left and right sides in this scape to fill the midground.
It is an extremely hardy plant and can grow well even in tanks without CO2 injection. it is a great choice for non CO2 tanks. If there are nutrients in the water column, the plant can be grown without a substrate. It is not picky about water parameters. In tanks with higher light, the internodes are shorter and the plant branches more profusely. It also creeps along the carpet when there is high light and open space.
Due to its ability to be trimmed at any height, the plant can be placed very flexibly in the tank. It can be trimmed to be a short bush just a couple of inches in height, or be used as a taller background stem plant filler.
Pearl weed as a taller midground bush in this tank.
Cut above an internode and plant top portion into the substrate. The base portion will sprout new growth heads. Over many trimming cycles, older stems will start to deteriorate and need to be discarded and replaced with fresh new tops.
Pearl weed bush (right side) in a low tech planted tank.