A procedure for feeding fish, such as rainbow trout, in a tank is disclosed. This procedure utilizes a suction sweeper on the bottom of the tank. By administering a predetermined amount of food to the tank and measuring how much food is not eaten by the fish, it is possible to reduce the amount of excess food. In addition, by cleaning the tank immediately prior to feeding and prompt recovery of the excess food, it is possible to recycle excess food without suffering from contamination, bacterial degradation or other unhealthy effects.