Over the past decades, demand for high-purity aluminium (Al) has increased in many sectors, like aerospace and automotive sectors, since it combines a high level of purity with the flexibility of controlled alloying, which allows for tailored enhancements of material properties. To accommodate the rising demand, primary Al production has significantly increased since the refining of secondary Al is constrained by high impurity levels, especially iron (Fe). A way to mitigate this problem is to add Fe-bearing intermetallic particle formers, like manganese (Mn). This paper investigates the influence of different Mn additions for low-Fe composition aluminium melts at a cooling rate of 3 °C/min, as the primary Fe-rich phases may differ and cannot be extrapolated. More specifically, the impact of filters, the Fe removal efficiency for different Mn additions, and the Fe-bearing intermetallic particles’ Fe removal potential. Fe removal potential was evaluated by combining intermetallic particle area fraction with their average Fe content. This was done by running Thermo-Calc equilibrium calculations to guide the planning of the experimental work. Then, running small-scale experiments with 8 kg of Al-11Si-0.5Fe alloy. The study concludes that the Fe-bearing intermetallic parties sedimented at the bottom of the furnace since the composition of the filtered and unfiltered samples from the top part of the melt was similar. Additionally, larger amounts of Mn are required to improve the Fe removal efficiency for low-Fe concentration Al-Si cast alloys since it improves the Fe removal potential and increases the amount of Fe-bearing intermetallic particles in the melt.