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HMF filter – advice?

Home Forums My Aquarium HMF filter – advice?

  • This topic has 0 replies, 1 voice, and was last updated 7 years ago by Matt.
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    Hi, Im new to aquariums and to the forum, and really looking for some advice on a HMF filter set-up.


    At my job we have a 5.6 ftx5.6×0.82 (1.7mx1.7mx0.25m) holding roughly 160-180 gallons (ca.600 L) with koi’s and goldfish and some algea eating fishes (14 total). In the middle towards the back there is a big rock, 2 feet high at least, serving as a fountain, which also represses alot of water.


    This pond has been neglected for several years with waste just accumulating and they think the circulating pump acts as a bio-filter which is clogged within a week, and waste was accumulating a a film over the fountain surface. Although they have carbon filter in the fountain pump, the first time i changed carbon, only black water was running from the carbon bag.


    So, I have now taken initiative to fix it up, as it also has a leak that is soon to be fixed.


    To make it more or less maintanance free I have been looking into a Hamburger Mattenfilter, written about on this site, however, with the shallow pond I have calculated the filter size to be too big to even fit in a corner! 4.2×0.85 ft. that should be mounted 2.6 ft from the corner. Here is a simple scetch of how I want it to be. Well, i just realized i did not account for the suppressed water in my calculations, but it should not be that much of a difference i would assume.


    The pump and heater can only fit in the back corner due to electric outlet. And there is only 1.3 ft clearance from each side in the corner out to the fountain. I would also like the fishes to be able to swim around the fountain, not blocking the back with a straight filter.


    Please, if anyone has any advise on the mat size or placement for such a shallow pond, i would really appreciate some help and advice. Also, i have concerns about full circulation. We have a Eheim 2252 that is 1200L/hr, which will create a velocity of 6.2cm/min over the filter ( calculated from 190 gallons or 722L).


    Thank’s a lot!






    Hi there and welcome to SF.

    First, I’d like to commend you for the initiative you are showing. 

    Having said that, I hasten to add that, keeping kois in 25 cm of water (never mind the footprint of the tank) is like keeping a horse in an outhouse. So even after fixing the filter, I’d strongly recommend convincing the responsible person(s) to either get a more suitable tank or more suitable fish!

    Now to your question. The footprint to height ratio of this specific tank really isn’t suitable for the corner version of the HMF. Here you’d have to install the filter mat over the entire back side of the tank. If possible at all the pump should be upgraded too, to about 1800 to 2000 l/h. If you want, I could draw a little something as soon as I get to my PC today. Two things I’d like to know: 1. are we talking about a glass tank? and 2. is the whole setup run by 1 pump or does the “fountain” have a seperate pump?



    P.S. A name would be nice too! I somehow can’t bring myself to call you “new fish”. :-D



    Hello Rüdiger, thanks for your fast reply!


    Well, my name is Helene and i’m located in Oslo, Norway. I have previously no knowledge of keeping aquariums, but i feel sorry for the fishes and the bad conditions they are in. So i have red a little bit here and there and getting a pretty good overview of some things.


    So, to your 1st question: The fish pond is actually submerged in a concrete floor with no glass walls. It does have a elevated edge and there is room to raise the water level 5-15 cm with proper sealing.   


    2nd: There are two pumps. The Eheim for circulation and a Mebner (Mephner) with the carbon filter connected to the fountain, but i’m not sure of the specifications. 


    I would be happy to provide some photos and accept your offer to draw me up “something” Smile.

    I’ll post back later on today.






    Hi R!


    Here are some pictures. I have made them a little brighter. I was told the koi’s pick a lot of the plants so thats why there are no plants either.

    I really hope to fix it up to minimum maintenance as this is just a part time job beside school and i might be leaving them soon. Prior to me cleaning the fountain rock there was a really thick layer with black, green, and brown stuff covering the whole surface where the water runs. I already see a brown layer of waste staring to form on the surface again. 



    With a more close up…..


    and the carbon pump.  The border you see on the wall seems very dark and almost black around the whole bottom. At first i though it was old carbon accumulating, but was later told carbon don’t accumulate like that. I have tried to scrub the walls, but they have small bumps and is really hard stained. CarbonPump.jpg

    and circulation pump in the back



    The water looks pretty clear at the moment, but just a small movement stir up a lot of bottom waste. I did buy a waste gravel cleaner, but with the bottom of tank lower than ground floor it didn’t work well Cool


    So the only thing i know is that the company is of course trying to keep costs down, and don’t want to spend a whole lot.


    I’m trying to write up a yearly budget for the pond and a procedure on when and how often to do different kind of maintenance and get it approved by the head of quality management.


    Previously they have had a local fish-store owner come and provide them with the koi’s. There was one pretty old at least 30cm in length he exchanged for 5 or 6 small koi’s. about two years ago. I have been in touch with him, but he had never heard of HMF, so i offered to help set it up myself. My boss has been on sick-leave for a while and have not approved my initiative, but several other employees do appreciate me fixing up.  So hopefully when i provide them with a concrete suggestion, they will listen.

    With a bio-filter i suggested to get rid of the big carbon pump, and change that for a smaller less visible, and to upgrade the lights, and of course more plants. I don’t know how much the filter would help reduce algae, but i see a clear problem that the morning sun result in more algae on the front wall by the carbon pump, while the back wall by the circ.pump there is a lot less algae as the fountain blocks the evening sun. In the top picture you can imagine the morning sun comes in from the right side, and the evening sun from the left side.


    You are the first one to say 25cm is too shallow for koi’s so this is new to me which i really haven’t thought too much of, sadly. What kinda fish do you suggest?

    Again, thanks a lot for your help so far, and still appreciate all the help to come!





    Hello H!


    I would not worry about the algae too much, they take over the function of the non existing plants and are in fact useful for your pond. They are rather a cosmetic problem. No filter will help you against algae. To prevent their growth you need to reduce nutrition, which is done by adding plants competing for them and/or by frequent water exchange (is their any water exchange done at all?).

    Moreover the “waste accumulating as a film over the fountain surface”  is most likely a biofilm consisting of useful bacteria and again algae.


    A correctly installed HMF would indeed be very low maintenance and could run for years without need for any manipulation.






    Hi Helene,

    I’m reading this at 23:43 Saturday lokal time. I’ll get to work on a plan for you tomorrow i.e. Sunday and I’m sure we can fix the filter problem. But there’s one thing as sure as h***, the kois will have to leave that puddle sooner rather than later! So, as they say, stay tuned! ;-)





    Hi Helene,

    unfortunately I am a bit short of time but I did two quick drawings, not very good but I guess they’ll illustrate what I’m about to explain. So first I’d suggest to get rid of that large rock/fountain thing, as it just occupies way too much of the valuable footprint of the pond.

    Then as I mentined above, if you want to use an HMF it’ll have to be the entire length of the basin. In the following drawing I have included the rock still, just to show how to set it up in case the people in charge want to stick with it.


    A = the Eheim 2252 with outlet C straight back into the tank

    B = the current fountain pump with outlet D for arguments sake connected to the fountain but ideally exactly like C

    E = filter mat

    F = Braces

    I hope that’s all rather selfexplanatory. The braces you’ll need to install otherwise the filter mat will be sucked inwards, towards the pump, thus allowing water to flow past unfiltered. Of course those braces can’t be solid but should rather look something like this:


    This way water can flow from the far end of the filter towards the pumps.

    With this set-up you get rid of the “carbon filter”, which is useless anyway and certainly not low maintanance at all. The second pump is integrated in the HMF, which should bring the flow rate close to where it should be without additional cost. The space between pond wall and filter sponge only needs to be large enough to acommodate the pumps. For that matter you might as well get rid of the 2252’s filter basket as it doesn’t serve any purpose in this set-up, only the pump head is needed. Same is true for pump #2. To install the whole lot you’d have to empty the puddle and of course find temporary storage for the fishes.

    Alternatively you could build something like in the following drawing from glass, acrylic or some pvc and submerge the lot as a unit.


    I hope that helps for the time being. If you have any questions, just shoot!! :-D



    P.S. There are, as always, different opinions about the requirements of koi. I do not keep any but I definitely would not keep them in 25 cm of water. I believe that 60 cm should be the minimum. If the tank is big enough one could include a shallow part, sort of a beach set-up. But the pond we are talking about does not belong into that category. ;-)  

    I would get rid of all the big boys and go for 20 – 30 specimens of one or two Notropis spp. They are colorful and lively!





    Thank’s for your reply knutschi! For the water exchange I really don’t think they ever used to change any water, but the receptionist used to top it up once a week from evaporation. Then she had to start top up every day and we realized there is a leak. So for many months now it needs to be filled up a few cm (2-4cm) almost every day. We fill up with tap water, which is safe to drink, although chlorine treated.

    As for the algae, maybe i was too hasty, but i have a feeling it’s too much accumulated bottom waste loose between the gravel, and without any plants and/or bio-filter, the eheim pump is not effective enough, and waste kept circulating creating the layer. That bottom waste is soon to be cleared anyways, so i’m trying to set up a healthy system, provided they listen to meConfused

    They do have a old testing kit with droplets which have been satisfying, but it’s been a long time since last i checked. The only high value was the hardness which i had to add up to 19 drops – each drop representing 1 unit, i think. So i had the laboratory test it (they have a water quality lab facility) and i think they said it was 8.


    And to you, R!

    Thank you very much for your input. I really have some organizing to do to set up the ideas for them. Unless the leak is connected to the fountain base i can’t see them removing it.  But the whole thing is to be emptied, leak fixed, and hopefully upgraded to my suggestions Kiss


    So, although it might take some time, i’ll try to post a update with pics of new pondLaugh


    and of course probably have some questions on the way.





    You might email Stephan Tanner at http://www.swisstropicals.com/Poret%20Filter%20Foam%20Pricelist.html  He’s our HMF guru here in the US.




    Thank’s for that advice, Dennisl. I just got email yesterday that next week they might start fixing the leak, so i’m all on it!







    Hello again,


    this took some time, but here is the new and improved pond.

    Only one fish died in the temporary tank we provided for them, however this was an old one with an ingrown and missing eye. The last week in temporary tank one of the plecos was really lifeless and seemed to die off, but this one is coming along.


    Please feel free to comment on the gravel color (English sea stone) not matching the granite. Does it really matter? Only one person commented on the gravel color, all others think its really nice. The more i look at it myself, the nicer it also gets Laugh


    The only thing missing is some water lilies behind the filter mat, and we have two big rocks that is going to be core drilled and submerged as caves/hiding place. And the lights are not connected yet.





    All fishes look happier with more space to swim. Even the active pleco leaps in the surface on its back and throw them self around.


    After looking up all fishes, we have 3 common plecos, one bristlenose, one featherfin, and one chinese algeaeater, including the koi and goldfishes. 


    5cm thick fine mat is installed, but i have ordered a EMW poret mat 20ppi in black.


    So, thanks for all the advice and help i got previously!!!!







    Hi Helene,

    looks good to me! ;-)

    I think the gravel is nice, especially because there is a contrast to the granite.

    As a caution: just be careful that the “big rock caves” don’t take up all the new found space your fishes are enjoying now!!!

    Well done!! :-)





    Looks great and love the innovative variation on the HMF. :)

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