The release of dissolved organic. carbon (DOC) by Daphnia pulex de Geer from six different algal species was evaluated using 14C‐labeled algae and analyzing the labeled dissolved organic matter. Up to 17% of the algal carbon ingested was initially lost as DOC from algae damaged during feeding. Only about 4% of the carbon from algae swallowed whole is released during ingestion. Additional DOC is produced by secretion from Daphnia and by leaching from their feces. More than 10% of the algal particulate organic carbon removed from suspension by grazing was transformed to DOC in the case of all food species except the very small green alga Stichococcus.