Chemically modified biomass of marine algae can effectively remove heavy metals from waste water. Australian marine algae (Durvillaea potatorum and Ecklonia radiata) based biosorbents (DP95Ca and ER95Ca) were developed and studied for their heavy metal removal properties from aqueous solutions. A two stage modification process substantially improved the leaching characteristics of the biomass. Batch equilibrium experiments showed that the maximum adsorption capacities of DP95Ca for lead and copper were 1.6 and 1.3 mmol/g, respectively. The corresponding values for ER95Ca were 1.3 and 1.1 mmol/g. These capacities are comparable with those of commercial ion exchange resins and are much higher than those of natural zeolites and powdered activated carbon. The heavy metal uptake process was found to be rapid with 90% of the adsorption completed in about 10 min in batch conditions. Heavy metal adsorption was observed at pH values as low as 2.0 and maximum adsorption was obtained approximately at a pH of 4.5. Both biosorbents were effective in removing lead and copper in the presence of chelating agents and other light metal ions in waste water.