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[APD] Re: new tank fertilizing #1
> A theory occurred to me as to why NO3 dosing on a new
> tank might cause
> problems. I have myself experienced a measurable NH4
> spike when I suddenly
> increased NO3 dosing. I assume that this was due to
> denitrification occurring in the substrate.
This should occur when the tank is new or not.
The denitrification and the nitrification of NH4=> NO2=> NO3 vs NO3=>N2 are separate.
Plant uptake is NH4=> then NO3.
If the addition of NO3 causes the NH4 to build up, was the growth rate the same? Was something else going on beside just the NH4/NO3 changes?
Take your plants out and try adding NO3.
See how long it takes for the NO3 to be removed over a week's time at 20ppm of NO3.
Add plants back, then see the rate of NO3 removal.
In an established tank, the NO3 removal should be faster.
See other post for NH4 testing without plants(since it's the bacteria as you contend).
The other issue: adding mulm from the start should take care of any NH4, unless you adding NH4(fish food or otherwise), where is it(NH4) going to come from? It's not from the NO3 addition, that I can tell you.
Plants prefer NH4, so do algae and will take it it up first, then go after the NO3.
I think something else is going on in your tank there if you had a persistence of NH4.
Perhaps the tank was N limited some, some other cause to slow plant growth down.
I cannot get a NH4 measurement. I dose 40ppm a week in my tanks of NO3 and may bacteria is well established as would be the case for NO3=>NH4 to occur(__highly__ anaerobic). You need to reduce 8 electrons to make NO3=>NH4.
> In a brand new tank, there are going to be areas of
> substrate that don't
> have healthy roots and are thus more prone to going
Err why is that going to be the case?
I can have a 10" deep sand substrate and not have it anaerobic.
I can have a 2" sub and have it anaerobic.
The difference is if I add organic matter(OM) that the bacteria will breakdown, thus use up all the O2, then the substrate will go anaerobic.
But you must have something there to use up the O2 to begin with and sustain this low level of O2.
Without adding OM, the redox/O2 will be the same as the above water column since diffusion occurs fast enough to maintain similar O2 levels.
If you added a bunch of soil, or had a lot of waste being added to the substrate, then the redox/O2 levels would be lower there.
It's rate/accreation dependent.
I add a little mulm and peat on purpose to lower the O2 levels and add bacteria from the start.
New subs and old subs are similar since I use the same materials to add to the new one.
I get no measurable NH4 levels.
> dosing could then cause excessive NH4 formation. I think
> we all agree that
> too-high NH4 levels can promote an algae bloom.
Why would heavy NO3 dosing cause this?
NO3=>NH4 takes extreme reducing conditions to occur.
This does not happen in our tanks. H2S formation and blackened subs will happen much sooner.
> Once a tank is established and the roots are pumping out
> oxygen, less NO3
> would be converted to NH4.
? No, see above, this requires intense reduction to occur and it would take a substantial time to form these bacteria layers(longer than other N bacteria).
Less O2 would be better, not worse for this to occur.
Also, once the plants are
> growing well they would
> presumably be better able to soak up excess NH4.
NH4 is the most available form of N.
That will help the plants to grow faster.
As long as the NH4 level does not become high enough to induce algae, we are fine.
> So in this theory, limiting NO3 fertilization at tank
> startup would not be
> about starving the plants, but simply avoiding having it
> turn into NH4.
We simply do not have that intense reduction occuring.
NO3=>NH4 takes 8 electrons to reduce, that's a hellva lot of reduction occuring:-)
I know it sounds nice, but the reality with this type of bacterial mediated conversion is, NO3=>N2 gas losses are much more likely. Your tank has something else going on, NO3=>NH4 mediated conversion is not it and it's certainly not going to occur in a new tank.
> As I said, I've seen the NO3 -> NH4 conversion in my own
> tank, so I know it
> can happen.
> - Jim Seidman
You are seeing something else, this reduction is the largest of about any there is in wetland soils. It does occur, but you'd have to add lots of OM 24/7. I'd rethink that assumption.
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