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Re: NO3 losses

> When I said N is secuestred by the biomass I wanted to  explain  the bigest
> part of N plant uptake is IN the tank, IN the plants you leave, in its rizomes
> roots and leafs, and not only on the part  you are trimming. (The plants,
> fishes and microfauna, they  not have the same weigth the day you set-up your
> tank or after one year)

But relative to the amount of N added and removed from the water column,
this is an insignificant amount unless you are removing large amounts
weekly/monthly or fish/critters/animals etc.
Also consider you are adding food for these aniumals also and some of the
waste ends up as plant "food" while some fish/animals eat some small amount
of algae.
The amount of N uptake from the water column is very low relative to the
plants and or algae.
> In a tank with a deep substrate is a lot of space for denitrifcation, everyone
> of us can constate ours sustrates bubbling, and these bubbles are mainly N2.

CO2 and O2 are far larger % of the gas evolved from the substrates. Roots
bring O2. O2 is used by Roots and expelled into the region around the roots.
ASll this O2 allows a large aerobic bacterial colony to grow. These aerobic
respire and give off CO2 gas.

> More space is available in every mature biofilm, even in very  oxigen rich
> waters.-
> The lost of N by denitrification,  (I,m remembering because at home I do not
> have bibligraphy) should be more or less 50%,

50%? Well the highest levels of denitrification I've found was around 2-3%
in Danish Estuaries.
See the denitrification rates of Saltwater plenums. Granted these are not
the same but I don't think they come close to the planted tanks.
We add a good deal of KNO3 every few days. Slat water reef's don't ever add
any NO3 source.
They also have huge _protein_ skimmers which remove guess what? Nitrogenous

A very simple solution to test this simply requires you to remove the
substrate and grow Riccia and/or plants lacking substrate root
attachments(Just have all the nutrients in the water column in an empty
tank). No substrate, no N2 losses.

I have such tanks running right now.
I can assure you, the NO3 removal is not due to the bacteria in any
significant levels(less than 1ppm a week).

A non Planted tank with a deep substrate should remove 5-15ppm or so
according to your figures a week. Adding roots which bring more O2 to the
substrate will make a worst environment for diazotrophic (Bacteria able to
split the triple N2 bond bond) bacteria, not better.

I have also used Reverse flow Under gravel filters for many years and the
NO3 uptake rates are similar to the tanks without such aerobic substrates.
Denitrifiying bacteria need specific environments to live and do well in.

Tom Barr 
> Best Regards
> Antonio Trias