Microalgae build the base of the food chain as being the dominant primary producers but also secure water purification and the function of freshwater ecosystem. Discharged toxicants can cause harm to aquatic microorganisms and get the ecosystem out of balance. Algal toxicity tests find their application in classifying chemicals regarding their hazardous potential and elaborate water quality criteria. Further, they are used in biomonitoring and assessing effluents to detect hazardous substances and lead to possible steps to intervene. This study focused on improving the standard microplate algal toxicity test based on a new freshwater microalga. The species Chlorella sorokiniana was investigated due to its ability to be fast-growing. With a growth rate of 2.20 d-1 C. sorokiniana was examined to be faster growing than Raphidocelis subcapitata (formerly known as Selenastrum capricornum and Pseudokirchneriella subcapitata) with a growth rate of XX. The new alga species were assayed on their sensitivity with three quaternary ammonium compounds (BAC, DTAC, DDAC), four reference toxicants (K2Cr2O7, 3,5-DCP, ZnSO4, CuSO4), and two active compounds in herbicides (Glyphosate, pelargonic acid). The results show lower or similar EC50 values compared to the standard species. With the finding in this study, C. sorokiniana can be suggested as new, more sensitive species for microplate algal toxicity tests with a reduction of execution time to 48 hours instead of 72 hours.