The need for cooling-water systems is common among industrial applications, but the treatments needed to keep them operating at peak efficiency can change from location to location and season to season. Quaternary ammonium compound (quat) biocides have an important role to play in balancing the performance, efficiency, and total lifecycle costs across many cooling-water-treatment regimens. And while quats offer benefits for algae control that other biocides do not, it is important to note that not all quats perform the same. A uniquely reformulated quat format (Figure 1) can bring all the benefits of biological control without the perceived drawbacks of other non-oxidizing biocide formats. That includes high-foaming or compromising effects on other water-treatment additives.