I run a mini on my 20G with just carbon. I did run it with foam and my powerhead with foam but my nitrates kept creeping up between water changes so I left them out and my nitrates dropped to zero. Been running with foam for about 3-4 months with no problems :confused:

The AC sponges will last for years, no need to constantly replace them.

Here's how my AC 500's (110's) are set up. One big sponge, two layers of fine blue/white media sandwiched together, then a thin double layer of polyester media for the very fine particles, topped off with a bag of bio-max rings. My water stays crystal clear.

The bio-max ring bags alone have enough bacteria in them to keep the tank stable after cleaning all other filter media. There are far less costly bio media items available than bio-max rings, but I scored these at an auction for next to nothing, and they have performed very well for me over the years. I also never replace the bio-rings, I simply lightly rinse them in clean dechlorinated water when cleaning the other filter media. Contrary to what Hagen states, they too will last for many years.


http://www.ida-may.com/other/ac5001.jpg

HTH

I have rings and sponges that I have been using for 10 or 11 years.

I couldn't agree with you more. Hagen sponges last for years as do the rings. I wouldn't bother with the other inserts they recommend as they're not needed. Cycle your tank, perform regular water changes and "clean" the sponges as Neil mentionned above and you'll be fine in a freshwater tank.

If you rinse/squeeze the sponge in a bucket of tank water during your water changes you also won't have to worry about killing all the bacteria in the sponge.