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Optimum current in planted tank

David Brooks wrote:

>To increase biological filtration would be presumably to help
>remove ammonia and nitrates from the water. 

Biological filtration (as the term is normally used, speaking of aerobic
bacteria, the only type of filtration supplied by fluidized bed filters)
does absolutely nothing to remove nitrate from the aquarium.  For that
matter, ammonia isn't removed either.  It is just converted first to
nitrite and then to nitrate.

> As I understand it this is
>what plants do and do better when there is more CO2 available to them. 

Plants _are_ of course capable of using either nitrate or ammonia.
(although their preferred nitrogen source is ammonium)  Adequate CO2 is
necessary, but so are all other conditions for growth... an adequate supply
of _all_ nutrients, and an adequate light source.


Carlos Munoz wrote:
>Frank, you might want to reconsider having extra biological filtering at all.
>If you have a heavily planted tank, the plants themselves are the best 
>biological filters for your tank.  They'll consume the fish's ammonium waste
>directly instead of converting it to nitrates.  


>I just have a Hagen 402 powerhead without any filter material in the "quick
>filter" cartridge that I got with it.  The cage keeps snails and small fish
>out of the filter, and the circulation is unimpeded by a filter.  I had some
>Kribs spawn a couple of months ago and for some time I had more "fish inches"
>than was recommended for my 45 gal breeder tank, but since I had enough 
>circulation to keep the surface moving (not *turbulent*, just moving), I had
>enough oxygen (thanks also, I bet, to the plants) to keep them all healthy,
>happy and growing fast.  If the plants didn't consume all the ammonium,
>bacteria grew on the plants and substrate to take care of the rest.  I had NO
>ammonia problems.  I *did* have a nitrate problem, but I think that was
>I had so many fish to feed.  

If you had a nitrate problem, it was, indeed bacteria that were doing the
work.  If it's the plants, there is no nitrate build-up because the
nitrogen is locked up in the plant tissues

>Extra biological filtering is a brute-force way of keeping ammonia in check. 
>You don't have to resort to it if you have a large enough plants-to-fish
>It *is* nice to have something filtering out large particles like floating 
>waste and leftover food, but it doesn't have to be used continuously.

If food is being fed in such quantities that the excess needs to be
filtered out, you'd better make sure that the mechanical filter is being
rinsed daily, or you will find yourself with very high ntrate and phosphate
levels as this material is broken down.
Karen Randall
Aquatic Gardeners Association