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Re: Mechanical Filtration

On Thu, 13 Apr 2000, Sylvia wrote:

> Wondering whether you do vacuum graveling while changing water?

I clean the tanks during weekly water changes and siphon off any readily
observable detritus.  I don't disturb the substrate while cleaning.  The
only time I've had much observable detritus was in a tank with fine sand
at the surface of the substrate - so fine that the detritus couldn't
settle into the substrate.

> I can imagine leaving out the bacterial filtration sponges and biowheels on
> the filters, but I can't imagine leaving out mechanical filtration material.
> My filters tend to slow down pretty quickly after a cleaning and within a few
> weeks are quite messy with gunk. (Whatever that is--I'm sure a small portion
> is bacterial population.)

In the tank where I'm still running a filter much of the material that I
clean out of the filter is probably the biofilm slime and it's bacterial
population.  Most of the detritus caught in the filter seems to break down
quickly in the filter and does not build up.  When I wait longer between
cleanings the filter gets clogged with slime, but it doesn't contain much
more detritus.

If you're going to use a mechanical filter at all then you really need to
keep it clean.  By that, I mean you should probably clean it at least once
a day.  Otherwise the filter traps the detritus in an oxygenated stream of
water where it breaks down quickly, releasing the oxidized decomposition
products into the water and producing the greatest possible impact on the
oxygen level in your tank.  I think it's much better to allow the detritus
to settle out in the tank and accumulate on top the substrate where it
breaks down more slowly; the impact on your tank's oxygen level is smaller
and the nutrients in the detritus can be cycled within the tank in more
readily available forms.  That's good for both the plants and animals.  Of
course, a dirty mechanical filter is also a bacterial filter, so if you
don't want a bacterial filter, then you *really* have to either avoid
mechanical filtration or keep the filter meticulously clean.

Adam Novitt mentioned that his empty Fluval canister acts as a trap for
sediment and serves as a mechanical filter.  I think that's a good
alternative to a standard mechanical filter because the trapped sediments
aren't held in the stream of water.  I've even put some effort into
building centrifugal separators that would enhance that effect, but there
are problems.  A self-cleaning mechanical filter like the (patented)
triangle filter might also be good for aquarium use.

Roger Miller