Kept as it has been, your feed certainly could be fed supplementally. It can't be completely destroyed by a few months of proper storage.
Maybe try a test for curiosity's sake. Throw a handful of the older feed "over here" and a handful of the fresh stuff "over there" and watch for a difference in fish preference. This wouldn't be any sort of a clinical trial, just something to observe.
Many organisms chose more nourishing food items over less nutritious stuff. An example I can think of is mule deer selectively browsing on specific sagebrush plants and not eating other sagebrush right alongside the favored ones. Nutritional analyses of the side by side plants have shown the favored ones to offer better value. Isn't nature wonderful?
Many species do not, of course, demonstrate that selectivity. Look at humans' propensity for eating junk food over more appropriate stuff.
You might have something to then post on the thread about "what I did at my pond today".
Anyway, I'd be interested in reading your observations. I imagine others here would be too.
