Predator size and diversity increase with pond permanence.  Consequently, changes in benthic communities with pond permanence are thought to be driven by trade-offs between the ability to exploit short duration habitats and resistance to intensifying biotic interactions.  However, few studies have explicitly tested how interactions between predators and prey change with pond permanence.  Field manipulations in New Zealand ponds suggested an unexpected decrease in community-wide predator impact with increasing pond permanence, which could be driven by interference between predator species.  We tested whether total predator impact was lower in permanent ponds with diverse predator guilds than in temporary ponds with simple predator guilds by conducting both substitutive and additive manipulations of invertebrate predator diversity and non-lethal fish cues in mesocosms.  Predator impact was enhanced with increasing invertebrate predator diversity and biomass (additive design), but the substitutive design (constant predator biomass with increasing diversity) confirmed that per-capita predator impact did not increase with diversity. The presence of fish cues reduced predator impact in the highest diversity treatment to less than or equal that of single species treatments in both models. These results indicate negative trait-mediated effects of fish on predatory invertebrates can reduce predator impacts in permanent ponds.