After 10 days, 4 of the 8 tanks were assigned to low-nutrient (LN) and the other 4 to high-nutrient (HN) treatment tanks (total n = 24 for each nutrient treatment). A mixed solution of KNO3 and KH2PO4 was supplied with a peristaltic pump to the HN treatment tanks at the rate of 11 mL h− 1 each. Nitrate (NO3−) is a major allochthonous nutrient for coral reefs and sometimes reaches a high concentration (Atkinson, 2011).