One day, we might look back and realize that this was the most dangerous consequence of all. The repeated use of algaecides doesn’t just create a cycle of dependency; it actively selects for a more toxic and resilient enemy.

Scientific studies have repeatedly shown that copper-based algaecides are more effective at killing safe beneficial algae than they are at killing the dangerous toxic cyanobacteria, so cyanobacteria gradually become dominant over time as you repeatedly use algaecides.

And it’s not just copper-based algaecides that do this. Peroxide-based algaecides do exactly the same thing — and the science behind why is both fascinating and deeply alarming.