If your after coldwater for outdoor ponds then you might struggle as most of the reputable LFS by me do not sell them during the winter months (this is because in the winter their metabolism slows down with the lower water temp, it's sort of like hibernation!) but as for tropical he's pulling your leg!
Fish in ponds stay at the bottom where the water is warmer (colder water at the top) and their metabolism slows right down so they don't need to be fed during the really cold months.