What kind of pump to use for a DIY filter?

[fish_chick]

I'm talking this kind of filter (http://www.youtube.com/watch?v=YZJBm89MuzU). What type of pump do you get to pump the water back to the aquarium? I'm looking to place a big order on petmountain but am worried i'll order the wrong type of pump. Thanks so much for any help! It's going to be for a 120 btw.