Micranthemum Micranthemoides, also known as Pearl Grass or Pearl Weed, is an excellent foreground plant to midground plant and will grow very fast in a Med to High Tech tank, but will also do well in Low Tech tanks as long as you use nutrient-rich soil, or supplement nutrients with root tabs (we personally grow them in sand with the Osmocote Plus Root Tabs we sell). You can grow Pearlweed as a carpet by trimming the plant often, or allow it to grow long stems reaching heights of 12".
To plant the Pearl Weed, you can either stick the stems into the substrate or tie it to a rock, and it will grow both horizontally and vertically depending on lighting conditions.
NOTE: One portion is roughly around what is shown in the third picture. These are sold as healthy trimmings, not in a pot.