Fish tanks require copper to maintain proper levels of nitrifying bacteria, the first two nitrifying stages require copper to convert stuff to the "safe" nitrog

Fish tanks require copper to maintain proper levels of nitrifying bacteria, the first two nitrifying stages require copper to convert stuff to the "safe" nitrogen that requires flushing to remove (unless you have real plants in the aquarium, then you rarely need water changes) - furthermore, copper is used to cure several fish diseases[0], so it it's impossible to be as bad as you claim. [0]https://smile.amazon.com/Seachem-67105650-Cupramine-Copper-100ml/dp/B00025K0QC/ https://smile.amazon.com/Seachem-67105650-Cupramine-Copper-1... for example