In response to the question and Cecil's reply: I know of no reason why a chelated copper would directly repel fish from a treated area, except if very low water-hardness levels allowed the copper to create an uncomfortable (and potentially harmful) environment for the fish. On the other hand, if the copper (or Cecil's reference "spray treatment") decimated the algae (or weeds) that the fish used as cover, they would likely relocate themselves to other areas where nearby cover was available.
Cecil: if (by chance) Hydrothol 191 was used in your observed treatments, fish would definitely depart the area for some amount of time - and the treated weeds would most likely reappear at some point. Wasteful? Maybe. Then again, I wash my truck to improve its looks. But, it doesn't take very long to get it dirty again. Just a synical thought.
