A highly interesting and recommendable ground-covering plant that was a rarity few years ago but got very popular in the aquascaping. It was discovered for the aquarium hobby around 2010 by Japanese and also South American aquarists. It was called Micranthemum ‘Monte Carlo’ after a locality in the Argentinian province Misiones, as well as “New Large Pearl Grass” and “Bacopita”. The plant has been identified as Micranthemum tweediei in the meantime. This Micranthemum occurs in Argentina, Uruguay and South Brazil, in wet places such as streambanks. It looks like a larger version of Hemianthus callitrichoides, growing flat on the ground, forming a compact mat, in the emersed and submerged form. Its roundish to elliptic leaves are a bit smaller and of a darker green than those of the similar Micranthemum umbrosum.

Micranthemum tweediei is much easier to grow than Hemianthus callitrichoides. Coming from subtropical areas with already cool winters, it probably tolerates temperatures below 20 °C, but that still needs to be tested. For planting, it is best split into single shoots or small bushes that are put into the ground with a little space to each other. The shoots begin to creep over the ground, often also burying themselves into the substrate, eventually forming an entire mat that can get several centimeters thick. It should be trimmed back timely to prevent detaching from the ground. When planted in an elevated place, loose shoots will bow to the ground.

This plant from southern South America is a versatily ground cover that is not very light-demanding. It can even be placed on the hardscape where it grows hanging down. It is also interesting as emersed mat-forming plant for paludariums and Wabi-Kusa.

• Family Name : Phrymaceae
• Origin : Argentina
• Height : 0.1-1”
• pH : 6 -7.5
• Temperature : 20-28°C