what type of air pump do i use

I got a gh waterfarm kit where you can make your own waterfarm useing a 3.5gal bucket & a 5gal. there are no instuctions at all but i think i can put it together just by looking at pics online.

anyway some seem to use a dual air outlet pump and in other pics of the waterfarm you only see a single outlet pump. which one do i use?

LAME! i just got a single outlet, hope it works