Dyes from different sources often behave with mostly toxic properties when they enter the aquatic ecosystem. The main sources of these toxic substances causing problems in the aquatic ecosystem are wastewaters of the textile and dye industries. The aim of this study was to examine the change of acute toxicity values of wastewaters containing dyestuff depending on time and color parameters. In this study, an acute toxicity test was conducted for 30 seconds, which is shorter than the time specified in the original Microtox test protocol. Thus, the results of the original Microtox Basic Test (BT), Microtox Color Correction Procedure recommended by the manufacturer (BT-CC), and the Microtox Basic Test-30 seconds (sBT) were compared, taking into account the effect of time and color parameters. There is a statistically significant difference between two groups: sBT and BT, and sBT and BT-CC (F = 4.919; p<0.01). The results of sBT have been obtained more rapid and more sensitively than other acute toxicity tests. The sBT, which is time-saving and gives correct result might provide some guidance as a pre-screening test and might be used in routine monitoring.