In sub-alpine ponds in central Colorado, long-term (decadal) cycles in the abundance of top predators (tiger salamanders) result in coupled oscillations in the abundance of benthic prey, including detritivorous caddisflies. In this study, we manipulated the density of caddisfly larvae (Limnephilus externus) in littoral cages to study how changes in their density affects detritus processing, benthic algae, and nutrient dynamics. Because detritivorous caddisflies can negatively affect algae through grazing, and positively by mobilizing detritus-bound nutrients, we compared algal biomass on grazed and ungrazed (suspended) substrates. Increasing caddisfly densities resulted in increased detritus processing and decreased C:N ratios in un-processed detritus. Caddisfly foraging reduced benthic algal biomass on grazed substrates, especially at the highest densities. High detritus processing was not accompanied by increased concentrations of total phosphorus or ammonium, nor increased algal biomass on ungrazed substrates. Our results provide evidence that long-term cycles in the top-predator in these ponds should have cascading effects on caddisfly detritus processing and algal standing stock biomass. Future studies in a closed experimental system will be needed to quantify the degree to which nutrients mobilized by detritus processing stimulate benthic algal production.