Bill I did not say that. Here is the sentence.

" In most waters CU (from CUSO4 but not from chelated copper)can build up in the pond bottom and cause problems with the food chain including fish."

Note the conjunctive "and". I have not seen any info (but would like to if it is out there) that says chelated copper residue will both build up in sediment and cause food chain problems. If it does I would like to know. The concept of chelated is that it is bound and unavailable i.e.
"Chelated" means "Inactivated" or "Sequestered".

I am no big fan of Cu in any of its forms and try to avoid it (but will use it under certain conditions) - see my post re manual removal above. I often kill small near shore patches of FA with hydrated lime but have noted caution as that raises the pH to 11 and can kill fish as well. Plus our waters can use the extra alkalinity.