Vinegar is a very commonly used to clean water pumps and other pieces of aquarium equipment, but be very careful when using it. According to some product manufacturers, using a vinegar and water solution to remove calcium deposits can also damage the plastic on the equipment or even the protective covering over the power cables. Vinegar is an acidic substance, so a generous dilution is needed to keep the solution from potentially damaging equipment. Not to mention, vinegar has a rather pungent aroma. As an alternative, try using straight warm water and a toothbrush, or even a product specifically designed to clean aquarium equipment.