We designed an experimental setup which permitted the selective exclusion of predatory Chaoborus larvae from mesocosms. With this new type of enclosure we could investigate the impact of Chaoborus on zooplankton and separate it from the effect of vertebrate predation by fish. The basic idea was to keep away Chaoborus larvae from enclosures by a mesh bottom or to let them penetrate enclosure bags open to the underlying water. The setup was tested in two very different lakes and proved to be adaptable to the specific lake requirements. Our design improves the simulation of lake conditions in the enclosures. First, predator densities are more natural and sec end, the animals are able to exhibit their normal DV
