Many shallow eutrophic lakes cannot meet the EU WFD-criteria in 2015 without restoration. The sediment P-pools must be reduced. Chemical treatment like aluminium-addition is an obvious technique in reaching the WFD-criteria. But there is no information available on the effect of chemical treatments on aluminium mobility, sediment stability or light climate. A laboratory flume experiment including three shallow Danish lakes was conducted. We measured the effects of aluminium, Phoslock (a commercial product), bentonite, and a combination of bentonite/aluminium. Each treatment caused a varying consolidation of the sediment. The largest consolidation occurred using Phoslock- and bentonite-addition followed by bentonite/aluminium-addition, whereas aluminium alone had no effect. Sediment stability thresholds were measured before and after addition. Especially Phoslock, but also bentonite and bentonite/aluminium increased sediment erosion threshold, with respectively 200%, 43% and 57%. Aluminium, bentonite/aluminium, and Phoslock improved the light conditions in the water phase, with respectively 60%, 57% and 50%, whereas bentonite created higher turbidity. Conclusively aluminium improved the light conditions but was very mobile and had no positive effect on sediment stability and compaction, whereas the combination bentonite/aluminium improved all parameters.