I think he was referring to feeding (did not notice you were feeding another food). Try this. Measure (get data)on a representative cross section of your fish population. If 10 % are big 40 % mid size and 50 % small then measure in those %. Out of 200 fish measure 2 large ones 8 mid size and 10 smaller fish. If you want a bigger sample then double the # measured ( 4 , 16 and 20) Chart them over time.