The study included the ecology and classification of non-diatom phytoplankton in the biological treatment ponds of a leather factory in the tannery in Baghdad. Water and algae samples were taken from three ponds within the factory during the autumn of 2025, with three replicates per site. Some properties (chemical and physical) were measured: water temperature, pH, total suspended solids, and nutrients, including phosphates, nitrates, and two heavy metals: chromium and lead. The results showed slight variations in temperature and pH (27.277-29.177°C and 8.200-7.267, respectively); total suspended solids were recorded at 47.000-80.467 mg/L, while the nutrients showed high concentrations. Phosphate ranged from 2056.600 to 4521.600 mg/L, and nitrates from 1424.333 to 688.533 mg/L. Heavy metals, particularly chromium and lead, were recorded at elevated concentrations, especially in the final treatment pond. The study diagnosed 19 genera, including 29 species of planktonic algae. Cyanophyta constituted the largest percentage (13 genera, 22 species), followed by Chlorophyta (3 genera, 4 species), while Pyrrophyta, Chrysophyceae, and Cryptophyta algae recorded a percentage of represented by one genus and species. The study demonstrated that blue-green algae were the dominant species, owing to their higher tolerance to pollutants present in the treatment basins. These dominant species can potentially be isolated and cultured for use in biological treatment applications