agreed.
Most places will sell you an airstone for aeriation in your tank, which is a crock. the water needs movement to stay aeriated, so usually the best thing to do is leave the spray bar (external filtration) across the top, or the head of the internal filtration near the top.
usually airstones are used to make a look in the tank, and nothing more. the air from the stones rushes to the top and pops making the o2 go outside the water, not in the water