The role of primary film formation in the colonisation of substrata by marine invertebrates was investigated in experiments conducted in waters of the Western Cape, South Africa. Surface‐bound antibiotics and herbicides were used to reduce proliferation of bacteria and diatoms respectively on test panels, while the primary film was enriched on other panels before exposure to the sea. The colonisation by invertebrates was monitored on these surfaces and compared to control treatments. The serpulidSpirorbissettled more readily where the primary film was well‐developed, but less discriminating barnacles(Notomegabalanus algicola)were capable of anchoring onto surfaces with only little bacterial mucilage. Our observations indicate that a well‐developed primary film was not essential for initial colonisation by barnacles near (< 10 m) an established community. A well‐developed film may be more important for barnacles at sites some distance from an established reef, suggesting that the primary film could mediate a factor originating from an established community that stimulates cyprids to settle.