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Re: Aquatic Plants Digest V3 #448

On 15/8/98 5:48 AM, Aquatic Plants Digest Aquatic-Plants-Owner at actwin_com 

Anthony Ciarochi asked:

>I recently read (either in this list's archives or on the Nature
>Aquarium page) that biological filtration is much less critical in a
>well-planted tank, as the plants are able to metabolize most any waste
>products produced by the fish.  Does thisreally mean that plants are able 
>to metabolize ammonia and nitrite, in addition to nitrate?

Not quite. Plants metabolise ammonium directly, preferring it to nitrate 
as a nitrogen source. Nitrite is produced by bacterial breakdown of 
ammonium, and nitrate by breakdown of nitrite. Any ammonium metabolised 
by plants never gets a chance to become nitrite, which also means it 
never gets a chance to become nitrate. In other words, plants can replace 
a biological filter by simply metabolising ammonium and removing the need 
to break it down to nitrate and nitrate.

A tank with a high plant and low fish load will actually utilise all the 
ammonium produced by the fish and will not require a biological filter. 
There are a number of people on this list, myself included, who 
succesfully run tanks without normal filtration. I simply take the sponge 
material out of an Eheim internal filter and use it as a pump head to 
provide water circulation and rely on my plants entirely. I never have 
measururable nitrite levels, nitate remains very low to almost 
immeasurable, and I only ever measure a trace of ammonium - not enough to 
ever cause problems. Keeping your pH on the acid side of neutral (around 
6.5 to 6.8, say) helps to ensure that ammonium is not a problem.

If you want a higher fish load, you may need a biological filter as well 
as the plants, but you will need a much smaller filter than would be 
required in a tank without plants.

A variation on this approach is the use of algae scrubbers as espoused by 
Walter Adey in "Dynamic Aquaria". Algae are plants and an algae scrubber 
is simply a filter based on algae maintained outside the display tank, 
somewhat like a sump.

David Aiken