When you are looking for an air pump, you will want to research what the head pressure is rated at. This is usually given in inches. The deeper whatever you are trying to push air through is in your tank, the more the pump has to overcome the pressure of the water at that depth.
For instance, an air pump at 6 inches of depth has to overcome less water pressure than an air pump at 18 inches of depth. So, the exact same air pump can put out different volumes of air depending on how deep you are running the item you are driving with it.
Obviously, at a certain point, the pump will meet the pressure where it can't supply a positive flow, which is called the maximum head pressure.
All this to say, just make sure you get a pump that can pressurize air volume at whatever the depth of your column tank, or however deep you are going to mount the sponge filter.
Hope that makes sense...