| abstract |
A method of raising sea-water fish is performed by raising the sea-water fish in water in a display tank which includes a device for circulating the water in the tank, a filtering material supporting plate having a sand-like filtering material containing calcium therein. In this case, the grain size of the sand-like filtering material is set between 2.5-3.5 mm. Coral sand is preferably used as the sand-like material, since it promotes the propagation of aerobic bacteria and converts ammonia and nitric acid to harmless materials and the above grain size exhibits better effect. This method can be performed by a display tank system including a tank for storing the water therein, a bottom filtering sections including the coral sand, an external filtering system disposed outside the tank, a feed-out tube for feeding the water in the tank to the external filtering system, and a mechanism for circulating the water which has been filtered by the bottom filtering section through the feed-out tube and the external filtering system into the tank again. The feed-out tube can be provided with a bypass mechanism for feeding the water in the tank to the external filtering system directly without passing the bottom filtering section. |