Effect of pH on malachite green removal ability: To study the effect of pH of malachite green solution on removal ability by Padina sp., 0.01 g dry wt. of alga was added in 10 mL of 5 mg L-1 malachite green in a 125-mL Erlenmeyer flask at pH rang 2-8. They were shaken at 120 rpm on a shaker at 25 °C for 3 h.