Hygrophila polysperma 'Sunset' ('Rosanervig')

Hydrophila polysperma "Sunset", in Europe sold under the name "Rosanervig", has its origins in the Danish aquatic plant nursery Tropica. One special characteristic of this variety are the white-coloured leaf veins. They are not the symptom of a nutrient deficiency, though. It is assumed that a virus prevents the tissue around the veins from producing chlorophyll. This virus specialises in this variety only and thus poses no danger at all for the rest of the aquarium plants. This variety of the so well-known robust Asian H. polysperma has become a very highly coveted aquarium plant.

This undemanding red-coloured plant is very interesting as it is probably the easiest plant of that hue in cultivation. It grows under almost any conditions. Temperatures between 18 and 28 °C, pH values in the range of 5 to 8 and a water hardness of soft to hard are tolerated very well, which shows how adaptable this plant is. It does not require lots of light and CO2, however, when provided with these factors its reddish colour gets more intensive. Iron also plays an important role for the reddish hue, too, as the plant colour tends to fade to shades of pale white if there is insufficient iron in the water column.

Like so many other fast growers, this plant tends to grow horizontally along the substrate. In many cases, this habit is caused by lots of light and helps the plant to cover as much room as possible before it resumes vertical growth. You can easily prevent this phenomenon by planting the stems very densely or by increasing the phosphate (PO4) level in the tank. Propagation and trimming are very easy. Just cut off a shoot and re-plant it in the substrate. Cutting back the main shoot results in many lateral shoots, and thus frequent trimming results in beautiful very bushy plants.

Hydrophila polysperma "Sunset", or "Rosanervig" is a red stem plant with lots of potential. Its highly interesting colour structure makes it a true asset in the middle- and background of the aquarium. Its relatively small leaves of around 4 cm length make it a suitable plant for almost all tank sizes.