The maximum filtering capacity ratings of both filters are advertised as the same: 20 gallon tank/ 100gph.
In my humble opinion, the Penguin filter has the advantage in at least 3 areas: Flowrate, O2 exchange & biological capacity.
Flowrate Experiment:
1 Clean AC20.
1 Clean 100B.
2 large buckets of water.
2 empty buckets.
The intake tubes on both filters are identical length, but the P100 tube is slightly larger in diameter.
If both filters are rated for 100gph, then even though the intake tubes are different diameter, they should empty the buckets in equal time.
Insert intake of each filter into full bucket, plug in each filter & see which filter empties it's bucket first.
After 5 trials, the 100B wins every time.
(Note: I should have timed each test, but I didn't think of it till just now. :wallbash: ).
O2 Exchange Experiment (pictorial):
AC20 surface effect for O2 exchange.
A freshly cleaned AC20 on a 10 gallon tank.
The AC20 output does go slightly deeper into the tank, with many small bubbles pushed to the bottom of the tank. For the best O2 exchange however, more surface action is better than deep water movement. In the picture, you can plainly see that the surface ripples barely make it across to the front of the tank.
Comparison shot #1:
http://www.plecofanatics.com/gallery/showphoto.php?photo=7467 :takepictu
Penguin 100B surface effect for O2 exchange.
A freshly cleaned Penguin 100B on a 10 gallon tank.
The 100B output is a little shallower, but tiny bubbles are still seen being pushed towards the bottom. As is evidenced in the picture, that slight change in the output angle does result in much stronger surface ripples that have no problem making it across the tank - in fact, fairly large bubbles regularly break against the front glass of the tank.
Comparison shot #2:
http://www.plecofanatics.com/gallery/showphoto.php?photo=7471&cat=500 :takepictu
Biological Capacity:
I estimate the Penguin offers the capability for almost double the biological capacity of an AC20. The P-100's Biowheel has a higher biological efficiency than the small bag of Biomedia "nibs" that comes with the AquaClear to start with. Then there's enough space in a P100B between the filterpad element and the Bio-wheel for almost 2 packs of AquaClear20 Bio-Nibs or some full size BioMax rings. Such as this:
http://www.plecofanatics.com/gallery/showphoto.php?photo=7642&cat=500 :takepictu
As a matter of fact, the mesh bag of BioMax for an AC50 will just drop in. All that biomedia, plus the P100's Bio-Wheel, there's plenty of surface area for a huge colony of BB -more than enough for an insanely overstocked tank.
An AC20 has a very limited amount of space for Bio-Media. There are only 2 ways to add any extra Bio-Media:
One is to remove the Carbon layer. (I do this anyway as IMHO, carbon isn't needed).
Like this:
http://www.plecofanatics.com/gallery/showphoto.php?photo=7643&cat=500 :takepictu
The second option is to reduce the size of the coarse mechanical filtration with a thinner sponge. (I do NOT advise this unless, the thinner sponge is accompanied by a layer of fine mechanical filtration such as 1/2" of filterpad.)
Either option will only allow for another 3/4 to 1 full package of AquaClear20 Bio-media "Nibs" or removing the original "nibs" and inserting an AC50 biomedia bag.
Greater biological capacity might not mean much to some, but for those overstocked small tanks, it could mean sparing the fish a nasty NH3 or NO2 induced death. It goes without saying that loading more biomedia won't do anything for the accompanying surge in N03 that would result. Unless it's a heavily planted tank, you'll still end up doing PWCs every 2-3 days.
Edit: I should mention that the P100 does have one area that could stand some improvement: mechanical filtration. It's filterpad/carbon pac cartridge is easily overwhelmed by particles & debris. This results in lower water flow & eventually will stop the Bio-Wheel from turning. I wish MarineLand would offer a replacement filter cartridge that would leave out the carbon, but increase the amount of filter pad or sponge material.
I cut open the pad along the top, remove the carbon & fit another patch of filter pad material inside where the carbon used to be, then fold another patch of filter pad around the outside.
Cleaning the cartridge is a snap though.
Remove the cartridge & replace.
Cartridges with my modification are easy to clean as well.
Simply replace filter pad material or rinse under hot water till clean.
There.
That's my 2 Canadian copper coins.
