Correct size air pump ?

hi, I made my 1st bubble cloner . 3 gal with this air pump -
http://www.ebay.com/itm/141342908511?_trksid=p2060353.m2749.l2649&ssPageName=STRK:MEBIDX:IT
it is too small, it wont bring any bubbles to the top of the water. about 2 gallon water is all I got in my bucket.
can someone refer me to the correct pump I need ? thanks

Any aquarium pump should work in 3 gallons even. I buy mine at the local Wally Worlds.

that's what I was thinking but this one don't cut it. may be a defect