Pond and waterfall pumps circulate pond water for filtration or waterfall applications. Pond and waterfall pump head and flow performance increases as the HP rating increases. Different housing materials can handle fluids for various applications. Cast iron is more cost-effective but less corrosion-resistant than stainless steel, bronze, and aluminum. Aluminum resists corrosion better than cast iron and is lightweight. Bronze is corrosion-resistant. Stainless steel resists corrosion better than other materials and handles a wider range of liquids.