Baetis rhodani is one of the most common Ephemeroptera species in European waters. The typical habitat of these nymphs is the rapidly flowing water. They inhabit from the spring (crenon) to the lower part of the rivers (potamal), where they in the gravel substrate of the stream's bed, but can be found also in lakes.

They are categorized as swimming nymph and can do it quite fast for short bursts. In the norm they have two generations per year, one emerging in the spring and another hatching between end of summer and fall. Therefore the nymph is almost a constant presence throughout most part of the seasons.
The lenght of nymph can vary between 5 to 13 mm.

Above: ventral view