Colonies of C. tenuissimum form white crusts on seagrasses, shells, and other substrata. Primary buds usually form distally from the ancestrula (the original settled larva), with the next buds forming proximally. Growth proceeds in both directions, and intermediate buds aid in forming a double fan shape that eventually becomes rounded. Zooids are oval in shape and measure 0.53 X 0.25 mm. Each zooid has a pair of short distal spines, and 5 - 7 pairs of lateral spines. The operculum is chitinous. The lophophore averages 0.475 mm in diameter and bears an average of 12 tentacles. Old colonies have areas where degenerate zooids are partially closed or calcified, and filled with storage products, while other areas within the colony have new or regenerating zooids with functional polypides.