A method for the automatic collection of fish feces is described. Drainage water from fish tanks is filtered through revolving hemispheric metallic screens which quickly remove feces from the water and propel them into a refrigerated pan, where they are immediately frozen. Operation of the system-requires minimal attention and is not time-consuming. As indicated by the total collection of an inert tracer, chromic oxide, this method enables quantitative recovery of feces and makes digestibility determinations possible, even by the direct method.