Abstract: An artificial algal culturing reef unit, an artificial reef unit and an artificial culturing and fishing area unit, aimed at raising or culturing algae, fishes and shellfishes, are usually submerged in a shallow sea zone with a depth ranging between 5 and 15 meters. These units are required to be resistant to high waves and fast oceanic currents usually encountered in such sea zone. Although concrete materials are suitable in consideration of its strength and costs, an alkali is necessarily emitted from their surfaces that is extremely harmful to diatoms and algae as well as fishes and shellfishes.