air pump vs. filter

Question
I recently purchased a 2.5 gal tank & kit, I noticed the manufacturer (All-Glass) had these tanks packaged with a filter or an air pump.  I opted for the air pump for no particular reason.  Is their a benefit for one over the other...or do I need both pump and filter?  If so, do you recommend an air filter for this size tank? At the moment I have one gold fish.

Answer
hi Julie:  A filter is usually better then an air pump because a filter can clean water and add air to water where as an air pump wont clean your water.  

If you are putting a Betta in your tank then the air pump is not needed as Betta can breath both surface air and extract air from water....

hope this helps... dave