Small fragments of the hydrocoral, Millepora dichotoma, were glued to PVC racks containing three different types of metals. The following groups of metals were deployed: electrochemically passive alloys - UNS S30403, UNS S31603, UNS S31254, UNS R50400, UNS R52400, UNS R53400 and UNS N10276; electrochemically active metal with no harmful biological effect- St-37 mild steel; metal alloys with biocidic effect - commercial copper and casting brass 70 Cu 30 Zn. The samples were
immersed in a coral reef environment, at 6 meters depth for a period of 3 months, between May-August 2000. An adhesive two-dimensional growth of the M. dichotoma encrustation layer on the metal surface was clearly observed in all the electrochemically passive metals. No two- dimensional development of the hydrocoral was observed on the mild steel. The tips attached to the plates of commercial copper and casting brass 70 Cu 30 Zn, were damaged and died within three weeks.