Since the subject of context has come up - in the context of water-living invertebrates, copper is poisonous in anything other than very low concentrations. Thi

Since the subject of context has come up - in the context of water-living invertebrates, copper is poisonous in anything other than very low concentrations. This is why copper containing solutions are used to kill snail and slug infestations in aquariums, gardens and elsewhere. Not sure why there is any confusion about this. Any aquarium keeper for example, knows to avoid copper religiously if keeping inverts.