Salpa fusiformis, sometimes known as the common salp, is the most widespread species of salp. They have a cosmopolitan distribution, and can be found at depths of 0 to 800 m (0 to 2,625 ft). They exhibit diel vertical migration, moving closer to the surface at night. They can occur in very dense swarms, as solitary zooids or as colonies. Solitary zooids usually measure 22 to 52 mm (0.87 to 2.05 in) in length. They are barrel-shaped and elongated, with a rounded front and a flat rear. Aggregate zooids are 7 to 52 mm (0.28 to 2.05 in) in length individually (excluding projections). They are usually barrel or spindle-shaped.