The glistening gold-color of these fishes made them much sought for as household ornaments, and the demand for them became so general that establishments were opened for raising them for the market. One of the largest and most celebrated of these places for gold-fish breeding is in Oldenburg, Germany, where more than a hundred small ponds contain the fish in all stages of growth, from the tiniest baby to the big stout fellow eight and even ten inches long. The little ones are carefully kept apart from larger ones, for the gold-fish is a wicked cannibal, and devours its little brothers and sisters, and even its own children, whenever it has an opportunity. At the same time it is a great coward, and will hide away from fish much smaller than itself that have the spirit to attack it. A gentleman who possessed an aquarium in which were several large gold-fish, once placed a tiny "pumpkin-seed," or sunfish, about the size of a silver half dollar, in the water. Watching anxiously to see that the gold-fish did not injure it, what was his astonishment to see the "pumpkin-seed" dart furiously at the larger fish, which huddled themselves in a corner, or scurried hastily through the water to hide among the stones and mimic grottoes of the aquarium! From that moment the "pumpkin-seed" remained lord of the field, scarcely allowing his companions to come to the surface, as they are fond of doing, or to take a mouthful of food until he had satisfied his own hunger. Finally he had to be removed from the aquarium, to save the gold-fish from dying of fright.
The enormous demand for gold-fish is shown by the fact that from the establishment at Oldenburg alone over three hundred thousand fish are sent to market every year. Their price varies according to their size and beauty, for there are grades of beauty in gold-fish as well as in all other things. They are very pretty household ornaments, and by caring for them and carefully watching their habits, boys and girls may learn their first lesson in natural history. If kept in a glass globe, nothing can be more interesting than to watch them, for, as Mr. White says, in _Selborne_, "The double refraction of the glass and water represents them, when moving, in a shifting and changeable variety of dimensions, shades, and colors, while the two mediums, assisted by the concavo-convex shape of the vessel, magnify and distort them vastly." Still, the fish may be healthier if kept in an aquarium, as it allows more surface to the water, and consequently more air and ventilation. In any case, fresh water should be given the fish at least every other day, and if the globe or aquarium be ornamented with rocks and water-grasses, the fish should be carefully dipped out once a week, and the rocks thoroughly cleansed from all impurities.