Bioerosion is a natural process occurring on all reefs although rates and agents may vary across the reef and together with reef growth which also varies, results in them being dynamic systems. It is the balance between these two processes which determines the overall shape of the reef together with physical and chemical erosion of the coral substrate. Bioerosion includes the removal of surface substrate by grazing organism (Acanthaster planci; Sponges) and the loss of substrate by boring organisms which produces a continual supply of lagoonal and inter-reefal sediments. While reef growth has been well studied (Barnes and Chalker, 1990), bioerosion has been relatively poorly studied. Although this situation is likely to be rectified, as reefs are increasingly being impacted by anthropogenic effects, which often results in changes in the balance between rates of reef growth and reef destruction, with the latter far exceeding reef growth in many parts of the world (Pari et al., 2002; Sheppard et al., 2002). This loss of substrate may have severe biological, economic, and social consequences each of which will be discussed later.