The removal of heavy metals from industrial waste has become crucial in order to maintain water quality levels that are suitable for environmental and species reproductive health. The biosorption of Zn⁺² and Fe⁺³ ions from aqueous solution was investigated using Ulva lactuca green algal biomass and Corallina officinalis red algal biomass, as well as their activated carbons. The effects of biosorbent dosage, pH, contact time, initial metal concentration, and temperature on biosorption were evaluated. The maximum monolayer capacity of Ulva lactuca and Corallina officinalis dry algal powder and algal activated carbon was reached at pH 5 and 3 for Zn⁺² and Fe⁺³, respectively, while the other factors were similar for both algae, which were: contact time 120 min, adsorbent dose 1 g, temperature 40 °C and initial concentrations of metal ion 50 mg·L⁻¹. The batch experimental data can be modelled using the Langmuir and Freundlich isotherm models. Thermodynamic characteristics revealed that the adsorption process occurs naturally and is endothermic and spontaneous. For the adsorption of Zn⁺² and Fe⁺³ ions, the value of G° was found to be negative, confirming the practicality of the spontaneous adsorption process, which could be helpful for remediation in the era of temperature increases.