[Πάνος]

"Algaecidal activity
A polymerizedisomer of glutaraldehyde known as polycycloglutaracetal is a fertilizer for aquatic plants. It is claimed that it provides a bioavailable source of carbon for higher plants that is not available to algae. Though not marketed as such due to federal regulations, the biocidal effect of glutaraldehyde kills most algae at concentrations of 0.5–5.0 ppm.[vague] These levels are not harmful to most aquatic fauna and flora. Adverse reactions have been observed by some aquarists at these concentrations in some aquatic mosses, liverworts, and vascular plants. "
http://en.wikipedia.org/wiki/Glutaraldehyde