Synthetic Ecology is a novel concept describing the design of de novo ecological communities for a designated purpose. This study is a proof of concept for harnessing Synthetic Ecology in expanding the scale of commercially relevant micro algae (Chlorella vulgaris) cultivation using stable Synthetic Ecologies in open environments as opposed to vulnerable monocultures. We focused on whether the grazing activity of zebra mussels (Dreissena polymorpha) would result in a consistent, and commercially favourable, dominance of Chlorella in cultures that were also inoculated with a competing and potentially invasive cyanobacteria (Synechocystis sp. PCC6803). The key result of this study was that in axenic mixed species co-cultures, zebra mussels had a significantly greater negative effect on Synechocystis cell numbers than Chlorella (P < 0.0001). The zebra mussels' putative preference for Synechocystis over Chlorella suggests they could be used to maintain the dominance of Chlorella in outdoor cultivation systems prone to contamination by invasive cyanobacteria.