Like other pleurocarps of running water, this very common moss is very variable in form and size and often doesn’t look like it is supposed to, especially when it is in habitats where the flow is intermittent and/or variable.
It’s not fussy about the pH of the water it lives in, but avoids highly acid situations. With such catholic tastes, it is a really common aquatic moss in all kinds of watercourses and standing water. When abundant, it is a reliable indicator of eutrophication.
If in any doubt about its identity, bear in mind that its leaves are always strongly concave and more or less ovate in shape, with a strong nerve and marginal teeth. Sometimes its leaves turn to one side and then it resembles Hygrohypnum luridum or even Hygrohypnella ochracea in passing. In spatey rivers, its lower stems are often denuded of leaves. It often has capsules and being a Rhynchostegium, these have a smooth seta and a longly rostrate beak, which helps to rule out Sciuro-hypnum plumosum, with which it often grows and can resemble.Read the Field Guide account