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HMF Building Plan

I had read a lot about the Hamburger Matten Filter - from hereon referred to as HMF. The HMF is said to:

  • Be a cheap filter to install
  • Create a (very) large filtering surface for (good) filtering bacteria to do their work and therefore function better than the average internal filter
  • Give you room for CO2 and Heating to be hidden in the filter
  • Not take up room outside the tank (one of my favorites)
  • Give opportunity for experimenting with aesthetics
  • Be big fun in combination with shrimps as the low water flow and filter bacteria give them plenty of surface to graze
Some of the things I personally found to be a downside were:
  • In a typical HMF, there is just one filter chamber. In typical external canister filters, there are 2 or 3 chambers
  • You have to build it yourself to create an optimal filter. That means having to glue inside your tank and thereby devaluing it a bit
  • There is no easy way to change the filtermat, even if it only needs to be changed once a year
This is the design I figured out in order to overcome these downsides.

As can be seen from the plan, there is a second chamber behind the filter-mat that contains ceramic rings that are normally found in cannister filters. The third room, the inner-most room of the quarter-circle design, contains the pump and can contain other equipment or additional filter materials. As can be seen I've modeled overflows to the final chamber.

It was my specific intention to build the filter in a 'closed' format, i.e. the chambers are closed and the filter can be placed in the corner of any tank without having to glue anything. The water pressure and weight of the soil should, in combination with the enlarged footplate, keep the filter in place.

I also included a curved 'barrier'  for the soil to be put up against. This doesn't touch the filter, So I can exchange the mat without having to move the soil.

Using the information on, it was easy to calculate if the filter I was about to build would obey the laws of building a good HMF:

  • a 10cm radius, and a height of 30cm (the height of the tank), would provide a filtering surface of h x w = 30 x w = 30 x (1/4 x outline) = 30 x (1/4 x Pi x radius) = 150 x Pi ~ 471 cm2
  • the pump capacity of the pump I ordered was 250 l/h. That brings the flow-rate to (250 x 60 x 1000)/471 = 8,87 cm/min. This is right about what it should be  -- again I used the formula on
    • In fact: I used the other formula for Q to find the minimum and maximum pump capacity that would drive me to the minimum and maximum flow-rate described. That brought me to a pump capacity varying between 140 and 340 l/h. I settled in the middle. 

This all felt good and I finished a shopping list:
  • Filter material (I used filter mat for pond-filters bought at a gardening center -- Intratuin)
    • The mat measures 120 x 60 x 2 cm, which is plenty of surface for the filter I designed
  • Lycra (I used 2mm thick material bought at the local DIY store)
    • The glas measures 120 x 60 x 0.2 cm. In hindsight, Plexiglas would be the better choice as it is better to be used in combination with adhesives and withstands heat better.
  • Tubing (1 meter at the aquariumstore (Heems))
  • 90 degree angles for tubing (2) (Heems as well)
  • Two suction cups to fix the tubing to the side of the tank (Heems as well)
  • Silicone Kit for use in aquaria (Finally found it at the hardware store: Gamma)
    • Shrimps are sensitive to chemicals, don't use regular kits!
  • Two cable chuts I had lying around will be used to clamp/fix the mat
    • I only use the part normally fixed to the wall. It is exactly fit to push the mat into
So, I finished shopping. The next post will be about the building process, along with pitfalls that I encountered.