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Re: filterless tanks

On Sat, 23 Jan 1999, Ed wrote:


> This brings up a concern for me, if the
> plants does a better job of filtration than conventional filters does
> this mean that filters are NOT needed on a planted tank?

Filters are not needed in a planted tank.

Well, not for the sake of the plants, anyway.  If you want to keep a heavy
fish load, then maybe you want a biological filter in addition to the
plants.  In either case, you still need to provide circulation.

To expand on this a little...  I think that a large part of the nitrogen
content in fish foods - including high quality prepared diets and live
food - is in compounds that aren't readily broken down to give
plant-available nitrogen.  I suspect (but can't prove) that most of the
phosphorus is quickly released to the water.

In a filtered tank the detritus containing the relatively refractory
nitrogen is removed and that may push the nitrogen:phosphorus ratio down.  
In an unfiltered planted tank the detritus stays in the tank (it usually
settles out in thick stands of plants) and that gives extra time for fish,
snails and bacteria to convert it to plant available forms.  That results
in a higher nitrogen:phosphorus ratio.

The upshot is that if you don't use filtration you might not need to add
nitrate to make phosphorus the growth-limiting nutrient.

Geez, ss that obtuse enough?

Running a tank without a biological filter is I think an exercise for
experienced aquarists.

Roger Miller