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<i>Salvinia molesta</i> D.S. Mitchell (Salviniaceae) is a damaging free-floating invasive alien macrophyte native to South America. The biological control programme against <i>S. molesta</i> by the weevil <i>Cyrtobagous salviniae</i> Calder and Sands (Erirhinidae) has been successful in controlling <i>S. molesta</i> infestations in the introduced range, however, there is some debate as to how biological control success is measured. This study measured the response of epilithic algae and aquatic macroinvertebrate communities in a <i>S. molesta</i>-dominated state and subsequently where the weed had been cleared by biological control, as a proxy for ecosystem recovery in a before–after control–impact mesocosm experiment. The restored treatment (<i>S. molesta</i> and <i>C. salviniae</i>) demonstrated epilithic algae and aquatic macroinvertebrate recovery during the “after” biological control phase, defined as similar to the control treatment. Comparatively, the impacted treatment (100% <i>S. molesta</i>) showed a drastic decline in biodiversity and shifts in community assemblages. We conclude that the biological control effort by <i>C. salviniae</i> facilitated biodiversity recovery of the impacted treatment. Furthermore, epilithic algae and aquatic macroinvertebrate communities were reliable biological indicators for measuring ecological impacts of invasion and ecosystem recovery following biological control, and thus represent potential tools for evaluating biological control success and ecological restoration.