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[APD] RE: Fe and optimizing the substrate
> There is a simple test to see this NO3=> N2 occur in anyone's planted
> Remove the plants and keep out in a tub/bucket etc for a 2-3 weeks or
> spare tank.
> Leave the substrate in the tank, use a small tank such as ten gal or
> so there's less plants to deal with storing while this is being done.
> Add KNO3 and measure the loss of NO3 over a week, then see how week
> does and then week 3#.
There is an even easier way, but I'm lacking a key piece of
information... do a nitrogen balance. Simply save your clippings over
a month or two, dry them, weight them on a good analytic balance (I do
have access to one, so I could do this for those local to me)... What
I am missing is an estimate of nitrogen in plant tissue on a _dry
weight_ basis. It would be important to return the tank to the same
state of "pruned" to get a good result. If lots of us do this,
systematic errors involved will be averaged out quite a bit and should
give decent agreement. But lets be realistic here, we're looking for
an order of magnitude effect, this should be very apparent if it is
The problem with removing plants to check: At moderate levels of oxygen
you have the 2NO3->N2+3O2 reaction occurring, to keep consistent with
the marine folks that do deep sand beds call this region the anoxic
region. At even lower oxygen levels, call this area anaerobic, you
have the 2NO3- + 11H+ -> 2NH4+ + 3H2O reaction occurring (opposite of
biofiltration). Removing the plants may drop the overall oxygen
concentration in the substrate and favor a reconversion to ammonia as
opposed to nitrogen gas, so if anything removing the plants might be
considered a low limit to denitrification... see latest issue of FAMA
Re: Plenums in marine tanks for more discussion about this... Deep sand
beds that are too anaerobic turn into nitrate factories.
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