Some species of fish like that of Rainbow trout can be trained to obtain their food with the help of Demand Feeders. Demand feeding System can be built in the laboratory with cheap and readily available components. Demand feeding System described in this paper is useful in feeding fish ad libitum. Even recorders and counters attached to Demand feeding System keep a record of time and frequency of feeding. Food dispensers are adjustable for desired quantity of feed at each trigger actuation.