[3] Tanymastix stagnalis can be most easy distinguished from other species in the order by the form of the males' antennae and frontal appendages.

[1] Like other members of the Anostraca, T. stagnalis swims with the ventral side upwards by beating its flattened thoracic appendages, or phyllopodia.

[5] In North Macedonia, T. stagnalis lives in pools only 20–60 centimetres (7.9–23.6 in) in diameter, and 10–20 cm (3.9–7.9 in) deep, containing a few litres of water each.

In all cases, the pools overlie acidic igneous rocks, and they are usually mineral-poor and retain some moisture in the sediment when they dry out.

[2] Like all Anostraca, T. stagnalis is a filter feeder, removing microplankton, microorganisms and other organic material from suspension with its bristly phyllopodia.

[1] Tanymastix stagnalis is sensitive to changes in the intensity of light, and respond to sudden shade by swimming towards the bottom of the pool, or even burying themselves in the sediment.

The main threat to them is perturbation of the habitat, in particular the introduction of predators such as the fishes Lepomis gibbosus and Gambusia affinis.

[1] Tanymastix stagnalis has a wide circum-Mediterranean distribution across Europe and Algeria,[1] stretching from the Iberian Peninsula in the west to south-western Russia in the east, and northwards through Germany[6] to Scandinavia.