Pond Boss Forums GENERAL QUESTIONS Water chemistry Aquashade, Phycomycin, Phytoplankton

Hydrogen peroxide is an oxidizer or oxidizing agent. For a technical description of an oxidizer see this from Wikipedia:
http://en.wikipedia.org/wiki/Oxidizing_agent

If you want a simplier definition do some more searching on the web. Hydrogen peroxide in releasing the extra oxygen molecule, the oxygen atom is available to combine with other mostly organic substances to cause a reaction. In the case of algae the reactive oxygen causes a breakdown of the outer layer of tissue of the algae. Some algae have stronger, thicker skin than others. Peroxygen chemistry works best on Cyanobacteria (bluegreen algae) that have thin "skin". Strong, highly concentrated hydrogen peroxide will cause discoloration of human skin and start to deteriorate - dissolve (eat into) the skin similar to sulfuric and nitric acids both strong oxidizers.