Colonies of this species form thin, light brown sheets of encrusting zooids. The growth of the autozooids is of particular interest. At the edges of the colony zooids bud into linear series extending away from the colony edge, then at a later stage autozooids from different linear series may meet, and new zooids start to fill in the gaps. This means that the zooids are arranged in a very irregular fashion. The outer periphery of the zooids is bound by distinctly marked shallow grooves. There are kenozooids positioned as space fillers here and there. The zooids are 0.6-0.8x0.3-0.5mm in size. The polypide is visible through the frontal surface of the zooid. The lophophore is reported to contain 17-20 tentacles.
Alcyonidium albidum has been recorded from throughout the North Sea, down through the English Channel to the French coast at Banyuls-sur-Mer and into the Bay of Biscay.
This species encrusts dead shells, hydroids and algae. It has also been observed on the large solitary sea squirt Ascidia mentula, in the Clyde Sea and at Oban, west coast of Scotland.
This species develops up to 15 oocytes per fertile zooid. These develop into cyphonautes larvae and are released via an intertentacular organ (Prouho, 1892).