Do benthic biofilters contribute to sustainability and restoration of the benthic environment impacted by offshore cage finfish aquaculture?

► Benthic biofilters were deployed under an offshore fish farm and in control locations. ► We checked the farm influence on fouling, wild fish and sediment near the biofilters. ► Fouling under the cages used fish farm-derived wastes, but at low efficiency. ► Wild fish were more abundant in the biofilters located below the cages. ► Despite these clear benefits, sediment quality around the biofilters did not improve.