The potential of a macroalgae Chara sp. was investigated as a viable biomaterial for biological treatment of Malachite Green (MG) solution. The effects of operational parameters such as temperature, pH, initial dye concentration, reaction time and amount of algae on biological decolorization efficiency were studied. Biological treatment of MG solution by live and dead algae was compared. The reusability and efficiency of the live algae in long-term repetitive operations were also examined. The batch experiments results revealed the ability of algal species in biological degradation of the dye. The biological degradation compounds formed in this process were analyzed by UV-Vis, FT-IR and GC-Mass techniques. The degradation pathway of MG was proposed based on the identified compounds. In addition, an artificial neural network model was developed to predict the biological degradation efficiency. The findings indicated that ANN provides reasonable predictive performance (R(2) = 0.970). The influence of each parameter on the variable studied was assessed, reaction time being the most significant factor, followed by temperature of the solution. (C) 2009 Elsevier Ltd. All rights reserved.