By submitting detritus s.L, consisting of the fractions particulate detritus s.s., mineral particles, mesofaunal elements, cyanobacterial colonies and other microalgae such as diatoms, to density gradient centdfugation (DGC) in Percoll and Ludox-TM the major part of detritus s.s. could be separated. Qualitative analysis of the fractions proved that the organic carbon content and (to a small extent) the nitrogen content of the fractions distinguished after DGC were higher than those of the detritus s.L before DGC, probably due to contamination with the gradient material. These results as well as the problems of quantifying the natural food of deposit feeders are discussed.