Autumn is a great time to add fish to your pond. It's cool so water holds more oxygen and that is important when you consider a koi or goldfish has to be subjected to a little cramped bagged environment for an hour or two while you transport them. It's also the time of year when koi and goldfish are more plentiful and prices are generally more competitive. Many koi clubs hold their annual koi shows during the fall and sellers who usually are not accessible are in town with koi fresh from Japan and from the breeders. Fall is the end of pond season. Unless you are in Florida or Southern California where the seasons do not change as dramatically as the rest of the country, water garden centers and pond stores are trying to whittle down their live stock for the winter so deals can be found more readily.