Shellfish reefs have been heavily degraded by eutrophication, dredging and overharvesting, leading to their functional extinction across Australia. This loss subsequently impacted key coastal ecosystem services, including water filtration and nutrient sequestration. To identify how restored shellfish reefs can maximise nutrient sequestration, 18 restoration sites were surveyed within the Moreton Bay Marine Park, with sites chosen to represent gradients in water quality, landscape connectivity, and sediment characteristics. Each site was restored using nine robust oyster baskets (ROBs; 400x400mm mild steel triangular prisms filled with recycled oyster shells) in a 3x3 configuration. We took sediment cores underneath ROBs, within the footprint of the reef and at control sites at least 50 m from the restoration site to quantify nitrogen accumulation, and quantified reef growth and fish assemblages every six months. We found significant correlations between nitrogen accumulation under reefs with environmental characteristics of the reef, especially oyster growth, and connectivity with surrounding ecosystems, especially seagrass and mangroves. Variation in fish assemblage structure also correlated with nutrient abating capacity under certain scenarios, indicating that fish can mediate outcomes. Results illustrate environmental context is crucial for determining outcomes of ecological restoration, and then planning for such variation can improve restoration practise.