EDTA
From The Aquarium Wiki
EDTA is a popular acronym for the chemical compound Ethylene-diamine-tetra-acetic acid. EDTA refers to a chelating agent that is widely used to sequester di- and trivalent metal ions. (It makes toxic metals non-toxic).
Chelated metals (made non-toxic to aquatic animals) are added to aquarium tanks to fertilise plants.
Typically Zn, Cd, Ni, Cr, Cu, Pb, and Fe EDTA.
