Aquarium pumps have come along way for the improvement of the aquarium product industry.  Previously within the industry it was essential for aquarium owners to own both an aquarium pump to aerate the water with oxygen as well as a filter to skim the scum from the water to keep it clean.  However, the new technology within the industry allows aquarium pump fish tank freshwater systems to hold firm with only one piece of equipment to filter the water and oxygenate the water at once.  These new systems pump water up from the water level adding oxygen to the water as the water exits the filter.