Palaemon varians

Palaemon varians, known as the Atlantic ditch shrimp and variable shrimp, is a caridean shrimp found from the Baltic Sea and the British Isles to the western Mediterranean Sea. It reaches up to 5 cm in length and is never found in fully marine conditions, instead living in brackish water.

In the aquarium
Sold by aquarium retailers as grass shrimp, they have a high tolerance of varying salinity and temperature levels ranging from 1 °C to 30 °C for prolonged periods of time. They will feed on any leftover fish food, algae or plant life and are generally peaceful by nature when mixed with similar sized aquarium life.