The maximum size of plastic bead ingested by Bosmina longirostris and six species of Daphnia increased with increasing body size of the animals. The relationship between the diameter (µ) of the largest bead ingested (y) and carapace length (x, in mm) is given by an expression, y = 22x + 4.87. This relationship could be used to predict which members of a phytoplankton community would be available as food for different‐sized species of filter‐feeding Cladocera.