I bought a new type of fish food yesterday and not reading the contents, which I should have, fed a small amount to my shrimp as well. They and the snails went to town on the food and there is not a single crumb left. However, looking closer at the food today I realized that it contains copper. I check the shrimp tanks and all the shrimp appear to be fine. Will one single feeding of food containing copper hurt them or is it rather the long term access of that type of food that will kill shrimp?