I just got off the phone with Marineland. You can basically use the GPH stated on the Penguins and the Aqua techs will be the same.
http://www.marineland.com/products/cons ... ilters.asp
Basically Penguins name their filters after the GPH they have, which is an easy and accurate way to get the right filtration.
The Penguin Minis are the same as the Aquatech 5-15 with 100GPH, actually good for about 10 gallons of water.
The Penguin 125 is the AT 10/20 with 125 GPH, again, good for a 10 gallon tank or a little larger.
P 170 = AT 20/40, good for about 15-20 gallons but this is where it can get ugly, they rate this good for a 50 gallon tank. This is actually no where near what should be in a 50 gallon, even more most fish types.
Then the Penguin 330 = the AT 36, and they rate this for a 70 gallon tank.
So you can see how much the filtration fluctuates. It can get real confusing....sigh