This test method is useful for rapid determination of viable active biomass concentrations in cooling tower waters. The efficiency of cooling towers is directly affected by the concentration of biomass in the cooling tower waters. As biomass concentrations increase, biofilm formation occurs resulting in a decrease in the efficiency of heat exchange in the tower. Current tests for monitoring the biomass concentration in cooling towers require at least 36 h for growth of the microorganisms on a solid agar surface for counting. Replication of microorganisms over the 36-h period before results are available creates an aqueous environment which is no longer represented by the data generated. Timely test results can assist in minimizing biocide addition to control biomass concentrations. Kool Kount provides data within hours to allow for more precise control of active biomass concentrations in the waters.