They certainly can. Andy had a pair of goldfish in a small outdoor pond of his own. One summer, hundreds of tiny wrigglers suddenly appeared in the water. Obviously they were baby goldfish and this was proved to be true as they grew bigger. In a few months, the survivors were an inch or so long. At the end of a year, they had grown much wider and most of them measured at least two inches long. This goldfish multiplication happened three years ago. The survivors are now shiny fellows of glistening gold, about seven inches long and quite fat around their middies. Goldfish as a rule refuse to multiply when kept in a small glass bowl. However, when a pair of them are kept in a large, properly run, glass aquarium, they can be expected to reproduce every year. Andy suspects that they reproduce more readily when kept in an outdoor pond and certainly they seem to grow much faster under these conditions.