In this basic form, a Hamburg-Matten filter is convenient and effective and a lot less trouble to install and maintain
than almost anything else I know. The foam rarely, if ever, needs cleaning beyond an occasional vacuuming when doing
a water change. If it does start to become blocked, you will know because the water level in the reservoir area will drop
below that of the main area of the tank. If that happens, you just take the foam out and hit it against a wall a couple of
times to loosen any trapped mulm! No rinsing required.
It isn't really suitable for display aquariums of course and for a “one-off” small DIY project obtaining the foam and
fitting it is probably more trouble than installing a traditional sponge filter. And, just like any biological filter, a
Hamburg-Matten filter must be properly “cycled” before using it with precious livestock.
I think that where this system really comes into its own is in multi-tank and breeding set-ups where you can use the
filter as a divider. Figures 2 and 3 show a couple of possible configurations.
These divided tanks have a lot of advantages. They are certainly a very flexible way to use your tank real estate for
breeding fish and raising fry because the dividers can be easily moved to create different sized spaces while maintaining
a single large volume of water. You can easily remove one or more dividers and keep them “alive” in a separate tank with
adequate aeration.
One final variation on the standard filter (one that I haven't tried yet) is to create a corner filter rather than use the
whole end of the tank. Figure 4 shows the basic idea.