A feeder for larval and juvenile fishes is capable of delivering an adjustable dose of microparticulate feed to selected locations, via pneumatic conveyance and control. A source of low-pressure dry gas is used to blow microparticulate feed through a manifold and into a selected one of a number of tubes. In order to adjust the portion dispensed by the feeder, an adjustable portion control is provided. Instead of a fixed sized ration cup a threaded recess is provided. Within the recess is provided a mating nylon set screw with an Allen hex head socket. By screwing the set screw in, or out, a user may increase, or decrease the volume of each dose.