Look at this 2 ways.
1st is the removal of detritus. This is done when the water goes through filter media such as floss, sponges etc. As long as what you use is toxic free you can use whatever you want. I use various stuff depending on the size of the tank. For instance I have a tank that I use for breeding. I have partitioned it with a medium size sponge such as you'll see in the back of tanks in your local stores with the actual pump behind it. That traps the larger particles before they get to the pump and recycled. If they aren't removing enough of the detritus use a smaller size sponge (more dense and with smaller holes in it) or use a large one with a small one behind it. This is common in most actual filter pumps where the filtration chamber has sponge with floss. Anyway, all that does is to trap the gunge.
2nd is the "garden" area where you grow the beneficial bacteria. On a good many systems there are ceramic noodles or plasic balls in a chamber that do nothing other than provide as much surface area as possible to allow the growth of bacteria. Having that in a pump gives a quicker build up of the bacteria and ensures that all the water in circulation gets in contact with the ceramics thus capturing toxic chemicals such as the ammonia which is broken down to nitrates and nitrates.
Whether the ceramics are in a filter pump is neither here nor there. All the bacteria will still build up on substrate and any rocks etc you have in a tank, but may not be as effective as most tanks have places in them that aren't as active with the water flow.
What I'm finding out from my new intended marine tank set-up is that it's the rocks and sand that do most of the bacterial work. Most of the rocks are like sponges in appearance with a huge amount of surface area due to it being riddled with holes. Of course a good tank still needs a means of collecting the detritus so filtration medium is used for that.
So, really you have both a filter and a bacterial garden doing different things and they aren't necessarily in a single chamber such as in a pump.
Just make sure you don't ever clean the ceramics with anything but chlorine free cold water. A quick rinse to remove any detritus is all you need do. The sponges are flushed out in cold chlorine free water too, but to be honest the bacterial growth on them is very small compared to that on the ceramics so I'd say it wasn't essential as long as the ceramic bacterial growth is undisturbed.
I will be checking it out for sure!
