The short answer is yes, there is quite a difference. And it’s important to understand the reasoning for the specially formulated foods. Fish food is designed to meet the needs of the fish based on the water temperature. So protein levels in the foods will vary.
Summer is the season when pond fish grow rapidly and spawn. Their metabolism is higher due to the warmer water temperature. During these higher temperatures, the goldfish and koi need a protein-rich food to aide in their body and fin growth. Pond fish use the amino acids found in the protein for energy and to make new tissue.
In contrast, spring and autumn bring cooler water temperatures. As a result, the pond fish’s metabolism is slower, causing them to be less active. Spring and autumn fish food is formulated to contain lower protein levels. Feeding excessive protein in this season does not benefit fish and is released into the water as poisonous ammonia. This becomes especially dangerous because at these cooler temperatures, the bacteria that help to consume this ammonia are inhibited.