Copper salts

Even in small quantities, copper ions are toxic to many small and microorganisms. With the exception of catfish, for example, fish can tolerate considerably higher doses for a short time, so that use as a remedy seems possible, but is not advisable due to late damage or accumulation of copper compounds in the substrate (due to the possibility that larger quantities may suddenly dissolve again with the corresponding catastrophic consequences).

Nevertheless, copper as a trace element is essential for animals and plants in very small quantities essential. Especially in chelated form (plant fertiliser), its toxicity is also greatly reduced (by a factor of up to 1000).