Bulk particle fluxes and organic elemental compositions were compared among sediment traps treated with different poisons and preservatives. The traps (3:1 open cylinders) were deployed for 1–2 months at 30 and 60 m depths in a coastal marine environment. The tested treatments included mercuric chloride, mixed antibiotics, sodium azide, formalin, chloroform, and salt, along with untreated controls. Fluxes of bulk particulate material and weight percentages of organic carbon measured for differently treated traps deployed simultaneously at the same depth both varied by an average of ±8% of the mean value. Great numbers of large (>850 μm) zooplankton swimmers were removed by sieving from bulk sediment trap samples treated with formalin and mercuric chloride, and to a lesser extent from those treated with azide and chloroform. The <850 μm “sediment” fractions of the formalin- and mercuric chloride-treated samples were characterized by slightly elevated %OC concentrations and lowered (C/N) ratios, apparently resulting from smaller swimmers that were not separated by sieving. Overall, problems involved with sample and treatment washout, and swimmer artifacts in poisoned traps affected measured fluxes and elemental compositions more than differences that could be clearly attributed to microbial degradation.