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Old 02-16-2004, 01:11 AM   #1 (permalink)
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I'd like to show you a filtration concept that has gaining popularity in Germany and Europe alike but which I couldn't find on any U.S.- pages yet. The principle is that one uses a foam mat and places it against one of the sidewalls of the tank. A standard aquarium pump is placed in the small gap(2 inches)between glass and mat.
Thus the water flows through the mat with a far lower speed but over a higher surface area than in conventionally sized canister filters (in which the current(>>5 inches/sec) usually is too high to establish a bacterial fauna. Olaf Deters published the concept of this rather DIY -like filtration concept on his page http://www.deters-ing.de/ and many aquarists "converted" to the HMF ("Hamburger Mattenfilter", to honour the region where it came from) . There is an English-language article explaining the basic principles:
The mattenfilter in English

which tells you more. Here I would like to show you a way of how to implement this idea in a display-aquarium.:

Original author: Jörn Carstens
Translation: Jörg Ortmayr
The original author gave written consent to use his article in this forum.

Construction of a cornered Mattenfilter.

The classical Mattenfilter consists of a foam mat which is jammed in between front and back wall of the tank, parallel to the one of the sidewalls. This principle, which is effective and simple, has been used in many breeding tanks, but has one disadvantage in display aquariums: It doesn't look quite well. One had to look at the front side, often coated with mudparticles, quasi directly into the "sewage plant" of the tank. Clever guys invented the cornered filter, usually placed as a quarter of a circle in one of the corners of the backside. Far away from the frontwalls it is placed far more imposingly.

But a new problem arose: How should one attach the mat ? One couldn't simply jam it between the sidewalls any longer because it tried to regain a straight form due to its elasticity. By this, water always leaked through in between mat and sidewall.

Existing ways for fixings

For stabilization small strips of glas were recommended which were siliconed to the sidewalls of the tank. Disadvantage of this methode: Not every aquarist is familiar with a glascutter und has some rests of glas, even the glazier isn't happy about such mini (?) orders. There always remains the feeling that blurry edges of glas remain. An alternative, plexiglas, available at any home depot, isn’t always easy to handle either. Especially the constant glueing with the panes makes problems, some leakiness always remains. Strips of glas and plexiglas hold the mat only in one direction, so there is only a hold against the pressure of the bent mat itself.
Mechanically better it would be to fix the mat on rails. Sometime, somebody got the idea to use a cablechannel for this.
The cablechannel consists of plastic, is available at any home depot, easily to work with and gives extra fixation to the mat because of its U-like profile.

Cablechannels as holding rails

This idea is discussed here and the simple construction of a cornered Mattenfilter on holding rails made of these cable channels shall be shown on photos. Other technical devices like heater and pump are built in, too.This is shown as an example in a rather small aquarium (50*30*30 cm) . There everything is rather cramped, of course. In all larger tanks the construction is a little bit easier, the special problems of smaller tanks is explained in the text.

Original material

Plastic cable channels are available for little money in the electro department of many home depots, usually in different diameters from 2 metres lenght on. Usually they are used for the installation of cables when they are built in subsequentially, aswell for installations over the plastering or when changes in the cablenetwork have to be done often, as they have a removable cap.
The cablechannels are made of plastics and can be shortened quite easily with an all-purpose saw or a "cutter"-Knife. The cutting shall than be treated with a sharp knife to remove the sharp edge. Afterwards, the channel can be siliconed into the tank.


First on has to determine the size of the mat. You get calculationtools at Olaf's website LINK (see the example section at the end of ths thread) or at JAN RIGHTER's translated site (english )) http://www.janrigter.nl/mattenfilter/
The mattenfilter in English

For the construction of a cornered Mattenfilter one needs:

* a mat in the correct size and thickness

* a cablechannel in the necessary dimensions, length = minimum 2x the height of the tank

* silicone

and these tools:

* a yard-stick
* multi-purpose saw (with fine saw-blade)
* a knife to remove the sharp edge (or an awl)
* a pen to write on glas (e.g. Edding)

And these devices for the aquarium

* a pump with power adapted
* heater
* if desired: CO2-system and co..

First steps:

The cable channel as it is sold can be seen on fig.1. In the middle one sees a small piece consisting of the channel in strict sense, and the removed cap (left side). The cap isn't used any more. The mat can be placed in the U-like profile of the channel.
For this project, we use a mat of 3cm (= 1.2 inches) thickness which is placed in a cable channel of 30 x 15 mm dimensions (= 1.2 x 0.6 inches). For thicker mats, larger cable channels have to be used, of course.

Fig. 1: left side: cablechannel as seen in the shop, middle: channel and cup separated, right side: mat in the channel.


After the necessary calculations to find out the sizing of the mat have been done only the radius of the quarter-circle has to be calculated. This radius is the distance from the corner of the aquarium to the middle of the channel. If you forgot how to do these simple calcualations, you will find a tool at Olaf's website.
The channels are then cut to the correct lenght. The lenght should be the distance from the ground of the tank until to one of the bearing sides. Often there is a small protruding gummed hinge of silicone between sidewalls and ground, and also between sidewalls and bearing strip. So it is practical to shorten the cable channel here a little bit or to leave free a small corner. Shortening usually is simpler. It doesn't matter if the channel is shorter here for a few millimetres, this is were the sand or gravel will be later.

Now that the lenght is set one has to mark the distance to the corner of the tank (this distance = the radius of the quartercircle) in order to silicone the channels in the correct position. I use as a correct measure the middle of the cablechannel. One millimetre more or less doesn't matter, the mat is elastically enough to undo smaller errrors. The cablechannels get silicone on their backside and are glued to the position marked before. The result should look like in fig.2. As long as the silicone is still soft smaller corrections can be done, the silicone “sausage”should really be consistend (?) so that there is no leak between channel and sidewall and that no small fish might get through.

Fig. 2: The cablechannels are glued, mat is still left.


Those who want can close the contact between cablechannel and sidewall with a seam of silicone, but this is not necessary for its functionability. Now the silicon has to dry, one day should be sufficient. These seams don't have to bear that much load like the walls of the aquarium themselves.

Adding technical devices

Now comes the mounting of the devices. In our example, we want to install a pump and a heater. Especially in smaller tanks there is relatively little place left behind the mat, it is rather narrow. Then it pays to invest some time to find the correct pump or correct heater (speaking of dimensions). For tanks larger than 100 litres (> 25 G) the place behind the mat usually is large enough to fit in any standard size pumps and heaters.

Fig. 3: Mounting of technical accessories


For the heater, there are usually only a few ways to place it. In these small tanks, one should try to position it not below the bearing sides so that the cable can go freely upward and one can adjust temperature, if necessary. So the small pump had to be placed below the bearing side. In this example the pump was mounted rather high above. When doing a water change, it will run dry (which can be accepted for a few minutes) or has to be stopped. On the other side, it can easily distribute the warm and rising water from the heater. If one installed the pump more below, as it is assigned sometimes, one would have to build a tube from the pump-outlet upwards, including two 90°-bends. There is no place for that here and it needs additional material.
Here a small garden hose is set upon the pump (it doesn't have to be a yellow rest of a garden hose like in the picture)

Fig. 4: Mount the hose on the pump outlet.


It is recommended to use a hose that is bent a little bit, so that the tank is flown through diagonally. That way one gets the best temperature dispersion. The hose should also be bent a little bit upward, so that one gets a small movement of the water surface. . One has to find out during operations wich is the best position. Now you make a crosslike cut into the mat where the hose is passed through. Then, or rather simultaneously, the mat is pressed into the two cable channels.
This looks like in Fig. 5.

Fig. 5: et voil* : the mat in front, Finished !


In these small setups one needs a little bit of skill and patience due to their narrowness, in larger tanks (and therefore larger cornered Mattenfilters) it is easier. If the dimensioning of the mat allows, a place of about 10 cm (= 3.9 inches) should remain, then one can still work rather easily behind the mat. .A view from above shows how little place is left in this "mini" tank.

Fig.6: Little place in a "mini" tank


In the space behind the mat one can mount the thermometer or the (yeast methode) CO2-outlet below the pump. In larger tanks one usually has more comfort. But one sees how simple a construction for a cornered Mattenfilter can be. As well from the materials needed as for the time. . It is recommended to fill the tank with water and let the pump work for trial. That way smaller incontaminations (like from solvents) are washed out and one can trim the devices, if necessary.

Masking of the filter.

At first sight, now one has a round box in a high intensity blue (depending on mat colour). Not everybody's favourite. But: one sees no longer the suction tube of the filter, heater, etc… in the tank because everything is hidden behind the mat.
But, no fear (?), this view will change. The bacteria which settle will turn the colour of the mat to a dark blueblack to brownblack- In the next figure one sees a 5 week old Mattenfilter in a 80 litres ( 21 USG) standard-size-tank without fish but with snails.

Fig.7: discolouration of the mat, total view


For comparison: in the upper area it is still a little bit lighter, here the waterlevel sinks due to evaporation, here bacteria do not settle, below one sees the darkened mat. During a waterchange, when the mat is dry, one sees that the colouration is from a brown organical film (fig.

Fig. 8: Colonization of the mat, detail


Those who want can place plants onto the mat. All plants wich are offerd to grow on driftwood or stones are acceptable, like javafern, javamoss or Anubias. For sure, others are fit aswell, one can test it out.
One can attach these plants with a toothpick or sew them with fishing line onto the mat. One can also place the javamoss on the edge of the mat and let it creep below. Fig, 9 shows how this looks in a 2.5 month old tank.

Fig.9 masking of a cornered Mattenfilter with plants, frontalview.


This filter is in a 60*30*30 cm tank (23.6*11.8*11.8 inches, 14.3 USG) and is overgrown with two javaferns "Windeløv", a small Anubias and javamoss. Fig. 10. shows how it looks from above.

Fig.10.: masking of the cornered Mattenfilter, view from above


On this picture one also sees how the pump was attached: It was simply jammed in between the heater and the sidewall in two blocks of foamed plastic. This has the advantage that its vibrations are no longer at the sidewall, the pump works considerably fainter. If you look well, you see that the formerly blue blocks of foamed plastic have discoloured aswell, so here a bacterial fauna has established, too. With these small colonized blocks one can easily inocculate a new mat, then the bacterial fauna develops much faster than in a "nacked" tank. Especially if sand or gravel and other material in a new tank are brandnew.


One can make a cornered Mattenfilter with only little material and timely efforts. Due to is bowlike construction against waterpressure it gets a high stability. The guide rail of the two cablechannels increases this stability even more.
A mat is rather fast colonized by bacteria. The mat can be masked by epiphyts like javamoss, javafern or Anubias. So the mat is integrated optically in the aquarium within a few weeks completely. Nearly all technical devices can be hidden behind the mat. Thus, the rather large consumption of space of this variation of the Hamburger Mattenfilter (=HMF) is relativized. It can be integrated without problems in large and small aquariums alike.

End of original article
Original German language article:
URL: http://www.deters-ing.de/Gastbeitrae...ttenfilter.htm
Last updated October 16th, 2003.

How to use Olaf Deters calculations tools. Until now, there are no translations I know of where one can simply enter his/her aquarium data and one gets results. So here is a step-by-step-process of how to use this site even if you don’t speak german:

First: We calculate in litres and centimetres. Please convert – if necessary - your tank volume from gallons to litres. That’s easy: 1 gallon=4,546 litres, 1 U.S.gallon = 3.78 litres
Write down the volume of your tank in litres .

Second: Go to

for Q; enter the volume of your tank in litres
n is the number of times the tank should the circulated per hour. Leave it at “2”
V is the flow of the water through the mat, it should be between 5 and 10 cm/minute . Leave it at 7.5
Press enter . What you will get is an area in squarecentimetres, to convert into squareinches: multiply with 0.155

Example: you have a 80 US-Gallons tank : that makes 80*3,78= 302,4 litres
Enter Q= 302.4 (mind the . )
Leave n = 2 and V = 7.5
Press enter, result is 1344 squarecentimeters
Multiply 1344 with 0,155 = 208,32 squareinches. This is the size your filtermat has to be.

Third step: Abolish those crazy units

If you want to find out if one of your existing pumps can be used for this method go to


For Volumen: enter again the volume of your tank in litres.
For n (the number the tank should be cycled per hour ) set “2 “ again

Press =

What you will get is a simple calculation V*n = Q and tells you the performance your pump should have. In our example with a 80 gallons tank (=302 litres) it is 604 litres per hour. If you now click on “suche” (=Search) you will get a list of pumps that have this size. If you click the two buttons to the left you can go up and down in this list.

Defining the radius of the bent mat (for the cornered Mattenfilter)
calculating the bent mat

Höhe Aqua
(cm) Pumpe
(ltr/h) v
Höhe Aqua.=height aqu. in cm.To convert from inches multiply with 2,54
Pumpe (ltr/h)= the performance of the pump in litres per hour. If you only know the performance in gallons per hour: divide again by 4,546 (U.K.) or 3,785 (US), resp.
V in cm/minute is the speed of waterflow through the mat. Should be between 5 and 10. So leave it at 7.5

What you will get as result “e” is the radius of your mat .
Our 80 gallons (US) tank gave us in the previous example the need for a pump of about 604 litres per hour (= 159.6 gallons/hr)
The height of the tank is 20 inches. That makes 50,8 cm (enter in “Höhe”)
For “Pumpe (ltr/h)” enter 604
V remains at 7.5
. e = 16 cm that makes 6,3 inches

The distance from the corner of the tank to the middle of the cablechannel should be 6,3 inches…

I would like to thank Olaf Deters and Jörn Carstens for their consent to use their articles.

Bye, Jörg

[This message was edited by Jörg on Mon February 16 2004 at 04:25 AM.]
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Old 02-16-2004, 04:36 AM   #2 (permalink)
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Jörg, thank you _very_ much for the great article on how to make a Hamburg mattenfilter. I've heard about these for some time now, and your article illustrates the concept perfectly. I've been wanting to try something similar in small killie tanks, using an airlift tube instead of a powerhead.

Well done!


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Old 02-16-2004, 06:37 AM   #3 (permalink)
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This is a very interesting article, thank you for posting it. I couldn't find a description of the type of foam that should be used. Is something like this blue foam appropriate: blue bonded foam pad or does it need to be stiffer like this: pre-filter foam
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Old 02-17-2004, 01:47 AM   #4 (permalink)
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Hi Neal !

The bluefoam pad looks too soft in my eyes, I doubt wheter it would stand the waterpressure, I would choose the prefilter blocks, although they are rather small (from 9 to 13") and expensive. The standard foam mat here is a blue polyurethane (=PUR) mat of 50x50x5cm in fine, medium and course qualtity (holes per squareinches),sold in petshops for about €15(19 US-$). I bought mine in a DIY-market (like Homedepot ?) were it was offered as padding/upholstery material for chairs(a rather unorthodox source ).You have to check that it is permeable to air by trying to breath through it(>open!< cell foam).

foam in fine quality:

The diameter of the coin is 1cm
this might be inappropriate when you have a very high load of debris or sand, but has the largest surface
foam in coarse quality

Here it takes longer until bacteria settle.
a comparison of an old (alt) and new (neue) foam

a used mat in fine quality:

I am working on the translated Mattenfilter-FAQ and am going to publish it ASAP.

@ Andrew: As you can see at Jan Rigters site an airlift tube works well. Seems to be the easiest solution for a group of AQs.

bye, Jörg

[This message was edited by Jörg on Tue February 17 2004 at 05:16 AM.]
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Old 02-17-2004, 05:01 AM   #5 (permalink)
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Guten Tag Jorg,

What a great update on this filtration method. They were started in Germany, I think, about 45 years ago. We had friends in Hamburg that tried them but they were very ugly in the tank as the foam went across the entire back. My mother didn't like the idea of keeping the dirty form inside of the tank thus we kept the Eheim canister.

These filters have a place in the hobby and thanks for the fantastic update. I am from Switzerland but can't remember anyone there trying this system back in the 1960's.


I try to keep the tank plain and simple but it never stays that way!
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Old 02-17-2004, 05:54 AM   #6 (permalink)
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I was wondering if this could be modified to use as a CO2 reactor? If the sponge matting were put across the top (but below the water line, of course) and the CO2 line were inserted through the top. The CO2 would bubble in and congregate at the top of the chamber and then as the water pump pushed the water out, the incoming water would mix in with the CO2.

Any thoughts - think it would work?
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Old 02-17-2004, 06:57 AM   #7 (permalink)
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Hi Tim,

The Mini-Vortex uses the priciple you describe except the foam is on the bottom of the chamber. A small powerhead swirls and breaks up the CO2, then it escapes through the foam at the chamber bottom. I have one and it works great.

You can see the Mini at Robert's shop.


I try to keep the tank plain and simple but it never stays that way!
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Old 02-17-2004, 11:13 AM   #8 (permalink)
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Hey Tenor1 -
I've seen the ones Robert has - one of my friends has one on a 20g and it works great!! I was just wondering if - because of the increased surface area - this could work on a larger (55g?) tank. I'm planning on a diy in-line reactor - but wondered if this might as good, if not better.
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Old 02-17-2004, 03:41 PM   #9 (permalink)
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The Mini is recommended up to 40 gallons. The efficiency is related to the size of the powerhead and the volume of the mixing chamger versus the foam. But with everything for a plant tank, there are tons of variables such as amount of light, plant ration, etc. You could test it out and let us know the variables of your tank versus the units results. In other words...You'd be our guinea pig, lol. Personally, I prefer to get everything for aquariums larger than recommended, like filters, heaters, etc. I think the unit is too small for your tank.


I try to keep the tank plain and simple but it never stays that way!
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Old 02-18-2004, 04:22 AM   #10 (permalink)
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Hallo!/(Grüezi Carlos!)

You are right,it is said that the "HMF" has been "invented" by Mr.Baensch, the founder of Tetra. But it didn't spread outside the Hamburg area until Olaf published the idea in the net : If you can read German you will find more (http://www.deters-ing.de/). And it has finally reached Switzerland, too..

As for the CO2-Injection: why don't you try this?
CO2 into Powerhead
CO2 gets chopped by the motorblades and the small bubbles dissolve fast in the water and do not reach the surface.


I finished the translation of the Mattenfilter-FAQs :

Mattenfilter FAQs

[This message was edited by Jörg on Wed February 18 2004 at 07:58 AM.]
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