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Re: Filterless tanks/Bacteria questions


You're dead right in your thinking.  If we run fish loads as low as in
nature, you don't need filtration.  Even if you don't, you don't
always need to filter the water.  In nature, the water is both
constantly replenished by movement and has waste both removed by algae
and plants and converted into less toxic forms through the
nitrification process.  Nitrifying bacteria will set up home on any
surface the meets their requirements to live (oxygen, food, etc).  The
amount of surface area that can be colonized by bacteria is primarily
what dictates what kind of fish load we can have in our aquaria.  The
purpose of biological media in the filter is to increase the amount of
surface area that the bacteria can set up shop in.  If you don't have
the fish load, or if you have another way of removing waste from the
tank (plants and water changes) you don't need a filter.  There at
least a few people on this list who have unfiltered tanks.  Mine is a
5 gallon that has no filter, no active circulation (the water does get
stirred up by the fish), and a fish load of one betta and two Yamato
shrimp.  I get occasional nitrate readings in the tank, meaning
nitrifying bacteria have colonized parts of the tank.  A betta is a
reasonably high fish load for this type of tank (at least for such a
small tank), so I also planted the tank fairly heavily, so much of the
ammonia and nitrate is used up before it ever has a chance to go
through the nitrification process.  A small powerhead would probably
increase the amount of nitrification as you suggested.  I am not 100%
sure, however, and would be really interested in hearing someone else
on the list comment.

Also, you're right about the Magnum filters.  A Magnum rep I met at my
LFS told me that they were only designed for mechanical and chemical
filtration.  Bacterica will still colonize the walls and other parts
of the filter, but not nearly as many as if you had a dedicated
biological filter.

Justin Collins


Sometimes I worry about being a success in a mediocre world.
-- Lily Tomlin

> Date: Sat, 19 Sep 1998 21:05:32 -0500
> From: Kudzu <Kudzu at airnet_net>
> Subject: Filterless tanks/bacteria questions
> I have had a question on my mind for a while now. As I understand it
> can set up in the aquarium gravel with no problem. Under Gravel
filters are a
> good example of this. Some filters have have a bacteria material bed
in them,
> such as floss or the ceramic cylinders in canister filters where the
> establish themselves.
> I read somewhere that Magnum filters don't have bacteria hosting
material in
> them because they prefer to let the bacteria setup in the tank. My
first thought
> was OK the bacteria sets up housekeeping  in the gravel in the tank.
Then I got
> to thinking if that is correct then why would we even need filters?
(I am
> thinking of ammonia only, not mechanical filtering) Why wouldn't the
> just set up in the gravel and do its job. The more I pondered on
this I kept
> coming back to the common element here seems to be water flow over
the bacteria.
> UGF flows water over the gravel and Filters threw the media.
> Do the bacteria need the water flow for oxygenation or for to bring
their food
> (ammonia) to them?
> Also Assuming that water flow is the important factor here in theory
wouldn't a
> power head or something else that caused a steady flow over gravel
on the bottom
> of the tank do the same thing?
> This is just a curiosity question that has been bugging me for a
while now.
> Jeff <*\\><

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