Hi Phil
I've used AquaClear 70's on 10g and 15g aquariums with the flow reduced. The added media and water volume helps.
To modify them for slower flow, you need to remove the little tab located on the grey piece of plastic called the Impeller Cover that fits inside the filter and it's on top of the motor/impeller using a Dremel Tool or a small drill sanding bit. This tap keeps the intake U tube from swinging all the way to the right to slow the flow. When you remove the little tap, the U tube will swing about 1/4" more to the right and slow the flow down even more. This intake hole changes the shape when used with the U shaped intake tube from an "O" shape to a "()" shape. This mod doesn't change the full flow rate. You still have that if it is needed.
This part is Part F Impeller Cover A16315 on page 9 of the replacement parts:
http://www.hagen.com/pdf/aquatic/Aquaclear_English.pdf
I use two foam filters with either a 100 mL bag of Purigen or Seachem's 'The Bag' with Purigen placed on top of the two sponges. The Bio bag is placed on top of the Purigen to hold it in place.
Also, some people have been using the 2213 Eheim Classic with a 2211 impeller for slower flow. The 2213 has a 6 blade impeller and the 2211 has a 3 blade impeller.
Also the Eheim Liberty HOB filters have added a thicker bio-foam that is washable to their line. This makes the media last longer. New Bio:
Left C