how exactly did you accidentally drop banana in your tank? just curious. personally i think a little won't hurt. maybe wait a while before you give him some more to see how he reacts to it. i don't think i'd feed peel tho, even monkeys in the wild peel their bananas...
I was kind of wondering the same thing but when I think about it, it's not french fries or anything like that, it's a banana. Good for the fish as a treat.