Throughout 2016 - 2021, a series of experimental studies on 137Cs uptake and excretion rate constants for the silver Prussian carp (Carassius gibelio) were conducted in the Chornobyl exclusion zone (ChEZ) under natural conditions. To confirm the metabolic parameters of 137Cs in the silver Prussian carp under strictly controlled conditions at different feed amounts real supporting laboratory experiments have been conducted. The excretion rate of the 137Cs from the silver Prussian carp increased with increasing feed amount from 0.0068 ± 0.0003 day-1 to 0.0085 ± 0.0005 day-1 at water temperatures of 26 °C. The biological half-life of 137Cs activity concentration in fish can be reduced by 2 times by increasing fish growth using clean feeding. The excretion rate of the 137Cs from the silver Prussian carp agreed with data collected in natural conditions in the ChEZ during 2016 - 2020 at different water temperatures.