For a successful algal biofuel production it is imperative to slash the cost of algal oil to less than $50/bbl. Use of municipal wastewater for algal cultivation could obviate the need for freshwater and the nutrients-N and P. It also adds CO₂ through bacterial activity. Though the wastewater remediation ponds are in use since long but it is essential to determine what makes some algae dominant biomass builders in municipal wastewaters. Chlorella minutissima Fott et Nova dominated the entire phycoflora year around and throughout the process of the wastewater treatment at the oxidation pond system of Wazirabad (Delhi) in India. The ability to grow so profusely in such varied and contrasting situations made this alga unique. Besides pollution tolerance, it grew heterotrophically in dark under acidic conditions and as a mixotroph in presence of light over a range of organic C substrates. It utilized both ammoniacal and nitrate nitrogen, survived anaerobicity, 5% NaCl and -10 bar of osmotic stress. C. minutissima grew at 4-11 pH and raised the initially set pH (5-8) by 1 to 3 units in 7.5 hours. It showed gigantism, largely kept afloat in presence of utilizable organic carbon, while flocculated in mineral medium and on aging. The alga also possessed potential for biofuel production. The studied parameters indicate why C. minutissima was a potential biomass builder in municipal sewage and could be used to determine which other alga(e) may serve the purpose.