The species exhibits some differences from the closely related Fritschiella tuberosa, which is primarily found in soil environments.

The type specimen was collected in Taiyuan City, Shanxi Province, China, in a freshwater aquarium containing ornamental fish.

The occurrence of compensatory base changes (CBCs) and hemi-CBCs in the ITS2 secondary structure further supports the classification of F. aquatilis as a new species.

It comprises numerous small, uniseriate (i.e., lined up in a single row) filamentous branches that radiate outwards.

The thallus of F. aquatilis either sinks to the bottom of the tank or floats on the water surface, where it can receive direct sunlight.