NEO index literally means: natural, energy-optimised nutrition. Behind this lies the ratio of proteins to fats in the food. Looking at the season alone, the fish would only need half as much protein in winter (2:1) as in summer (4:1). But because not only the season (meaning the water temperature), but also the size and age of the fish, and food function (e.g. growth food = ProPond Growth) play determining roles, the der NEO index has been developed to deal with all these factors in one.
With JBL ProPond Spring you can clearly see that the NEO index alone is not yet decisive: The NEO index for spring and autumn food is identical at 3:1, although the food composition is totally different! Because spring and autumn have the same water temperatures the proper protein/fat ratio is 3:1 but the purposes of the foods are very different and therefore also their composition: In spring the fish need to be made fit and pepped up after the stress of winter, to fend off spring viremia etc. In autumn, on the other hand, the fish are expected to live off their fat reserves to stay healthy through the coming winter. Furthermore there is the different sinking behaviour of the food: In spring the fish become active again and may come to the water surface for feeding (this is your opportunity to check them for any diseases). That’s why the spring food floats. In autumn however the fish need to relax and eat at the bottom, Therefore the autumn food is designed to sink.