I bought the pro 110 and so far it's great and has lots of room for other filter media like polishing pads and nitrate pads or what ever your tank needs. I put it on my new 75 gallon aquarium with african cichlids in it and I'm running it with an under gravel filter so far I'm not having any issues but I haven't tried to over stock it yet. By the way the price was amazing compared to similar products only 59 bucks and I ordered it online so I was able to save about 25 bucks on that price threw petsmart.
