Myriophyllum spicatum

Eurasian watermilfoil, Myriophyllum spicatum, is widely distributed in Europe and Asia but is also found down to the African tropics. It is the most common of the three Myriophyllum species native to Germany. It has been introduced into North America, where it has formed hybrids with native species that are closely related to it, and they have become invasive aquatic weeds in the USA.
M. spicatum is frequently found in the aquatic plant zone of nutrient-rich lakes and rivers given that they are not too heavily polluted. In summer, it sprouts flower spikes that grow out of the water, and which gave M. spicatum its species name (spica = spike).

Myriophyllum spicatum is mainly known as hardy garden pond plant, but grows also well in coldwater or temperate aquaria. It is a very fast grower and thus has to be trimmed quite frequently. Its finely pinnate leaves are medium green, the stems are usually of a brownish red.
This milfoil is not as decorative as most other species of the genus Myriophyllum that are kept in aquaria, mostly because the distance between the leaf whorls is rather large, while the leaves are relatively small. However, it is a wonderful plant for tanks layouted with natural biotopes in mind.

The Eurasian watermilfoil is also recommendable for garden ponds. In hard water it tends to form whiteish limestone crusts on the leaves due to biogenous decalcification.