[1] Nitellopsis obtusa has long, fairly straight branches arranged in whorls, attached at nodes to the stem at an acute angle.

The oogonia (female reproductive structures) form at the base of upper branchlets and orange to red oocytes can occur, which help distinguish this alga from the rather similar musk-grass and brittlewort.

[2] This alga grows in freshwater to a depth of over 4 m (13 ft),[1] on soft substrates such as silt, sand and accumulations of detritus.

It tends to grow in deep, slow moving water where other plants are scarce, typically near docks and marinas.

[1] It is known from only a few sites in the British Isles,[3] and these include Cosmeston Lake in the Vale of Glamorgan.