Referring to the use of Mattenfilters, I was reserved in the beginning because of a 'natural opposition to simplicity'. Since I'm interested in filtration systems, I've read some literature about this type of filtration. I don't use it because the only tank left isn't suited to install it, but if I had to install a new tank, I would certainly chose this type.
In fact, we read all the time about denitrifying bacteria (2 or 3 species) and in the best case an anaerobic species, but the biological environment in a filter seems to be much more complex. I read somewhere that the above mentioned species represent only a very minor part of the biomass present in the filter. The mattenfilter can be interpreted as a highly efficient gravelfilter, based on the same principle. Building up a kind of mulm where a huge variety of microscopic live is filtering the water. Potable water is also filtered on the same principle. In nature, filtration is performed partially by the bioactivity in the mulm present in the upperlayer of the bottom. (I'm not a biologist, so if I'm telling stupidities, please correct me).
Crucial seems to be the flow through the mattenfilter. Should be between 3 and 10 cm/min. If the speed is higher, micro-organism will move to places with lower throughput.
On the website of Stendker Discusfarm in Germany, you can read that they apply this system since years and that they didn't clean their mattenfilter the last 25 years.
Another type of filter, based on the same principle but more sofisticated and that is only applicable to large public aquariums today, is the DyMiCo system (Dynamic Mineral Control). Based upon the same principle, but a computer is favoring aerobic or anaerobic filtration depending on the measurement of Redox, pH, etc... Not applicable in the tank of the common aquarist, but the principle is very interesting and put another light on what filtration is (or should be).
Have a look at their website and dream of this kind of installation on your tanks.
http://www.ecodeco.nl/producten/dymico- ... steem.html
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A friend of mine works at the Antwerp Zoo aquarium, where they are using succesfully this filtration as well on salt as fresh water. From an ecological point of view, they also succeeded to reduce the amount of waterchanges.
In the 90's Professor Jaubert used a much more basic system at the Aquarium of Nancy in France, known as the 'Jaubert method' in reef tanks. To my knowledge, this isn't applied anymore, but not unefficient for that reason.