Looked up EarthTecQZ and it uses uses cupric ion copper to kill these mussels. Cupric ion copper is apparently also not real good for fish. The below is from google when I looked up cupric ion copper. Things that make you go hmmmmm.
Cupric ions (\(\text{Cu}^{2+}\)) are highly toxic to fish, causing acute respiratory distress, gill damage, and mortality at low concentrations (10–20 ppb in soft water). Copper acts by irritating gills, inducing heavy mucus production, causing hypoxia, and accumulating in tissues like liver and kidneys, often resulting in lethargy and death