Aquatic plants can remove heavy metal contamination from the surrounding water. This study examined the ability of Microspora (a macro-alga) and Lemna minor (an aquatic plant) to remove soluble lead and nickel under various laboratory conditions. Microspora was tested in a batch and semi-batch process for lead removal. L. minor was tested in a batch process with lead and nickel to examine the potential competition between metals for adsorption. The Microspora was exposed to 39.4 mg/l of lead over 10 days. Results show up to 97% of the lead was removed in the batch process and 95% in the semi-batch process. Initial concentrations below 50 mg/l (a dose that kills the algae) had no effect on the final concentration. The L. minor was exposed to lead and nickel using a full 3(2) factorial experimental design (nine experiments, plus replications). Initial lead concentrations were 0.0, 5.0, and 10.0 mg/l, and nickel concentrations were 0.0, 2.5, and 5.0 mg/l in the experiment. Overall, L. minor removed 76% of the lead, and 82% of the nickel. No synergistic/antagonistic effect was noted for the multiple metal experiments, in terms of metal removal. (C) 2003 Elsevier Science Ltd. All rights reserved.