i use filstar xp2, xp3, and fluval 404
i use them because they have good flow rate and keep my tanks vry clean, and are vry easy to use.
i have an xp2 on my 38 gal, xp2 + fluval 404 on one of my 75 gal tanks, and xp3 on my other 75 gal tank (turtle tank)
and when i get my 125 gal i will use 1 or 2 xp3's or an xp3 and an xp2.