Hygrophila serpyllum

Hygrophila serpyllum is a small, creeping plant that is widespread in India. It colonises various wetlands that are periodically flooded and fall dry. This species is very different from other Hygrophilas in the aquarium hobby. Known to science for a long time, it has only become known as an aquarium plant in recent years. In the underwater form, the shoots grow creeping and branched, also hanging down from an elevated planting site, and root at the stem nodes. They form a mat at least 3 cm high, or a broad bush over 5 cm high if there is relatively little light. The approximately 1 to 1.5 cm long, roundish leaves are reminiscent of those of pennywort (Lysimachia nummularia), which however grows upright submerged. The stems are very thin but relatively tough.
In its emersed form, the plant also forms a small-leaved mat, but also upright flowering shoots with several small white-blue flowers. The specific epithet serpyllum, ‘wild thyme’, refers to the appearance of this Hygrophila, which forms low, richly flowering mats in the terrestrial form.

The Marsh carpet is a fairly easy, relatively fast-growing aquatic plant. It makes no particular demands on pH value and water hardness; the CO2 requirement is moderate. A complete supply of macro and micronutrients via the water column is very favourable for growth. Light requirements are also moderate, but strong lighting promotes low, creeping growth. It is best to place clumps of several shoots at some distance from each other in the substrate. The creeping shoots will form a closed mat over time. It is also possible to grow a wide bush, especially with moderate lighting.

The little-known Hygrophila serpyllum is a beautiful addition to the aquarium flora. This easy ground cover is somewhat reminiscent of Micranthemum tweediei, but has much larger leaves.
This Hygrophila from India also looks very interesting as an emersed plant for emersed setups such as well-lit paludariums and wabi-kusa, as it grows into a mat covered with lots of small white and blue flowers.