[APD] Re: new tank fertilizing

[Thomas Barr <tcbiii at earthlink_net>]

>How long is that? I honestly don't know how fast denitrifying bacteria grow.
>But if you're fertilizing the plants, then the bacteria must have all the
>nutrients they need to grow too.

Scott H. writes:
>>"If there was a large mass of such bacteria, shouldn't they
>>then be turning nirates back to nitrites? Isn't that one of
>>the features of anaerobiec bacteria?"

>There's a whole denitrification cycle:
>NO3- -> NO2- -> NH4+ -> N2

Err, do you have any idea what amount of reducing power is required to reduce something 8 electrons?
It does not exist in your tank and in a soil tank either.  

NO3=> NH4 is one set that requires serious reducing power(lots of OM!!) (- negative)200-300mv range
NH4=>NO2(aerobic, say +400mv)
NO2=>NO3(as above)
NO3=> N2 gas(200-300mv)

H2S reduction, ~100mv 

You'd have to prevent all flow/flux in/out of the substrate to have this occur.
Not likely. You'd also have H2S and CH4 as well as NH4.

>Just as with nitrification, different bacteria handle different stages, and
y>ou can have incomplete processing where the cycle doesn't finish. In my
>tank, I never saw very high nitrite levels, although there may have been a
>spike that I missed. But given the NH4 spike, much of the nitrite must have
>been converted to ammonium.

No, given the conditions required for NO3=>NH4, and the lack of plant uptake of NH4(plants will use NH4 first, then NO3, not the reverse), it's far more likely your tank stalled a little and you have a confounding factor/s related to growth rates. 

Robert Ricketts writes:
>>When ammonia or nitrite
>>are produced in the substrate, there should be enough oxidizers (facultative
>>or aerobic) at higher levels of the substrate to oxidize any leakage before
>>it hits the water column."

Then there is that issue as well.
You are out of layers and would have H2S formation occuring above if you had NH4 reduction occuring(bottom).

>Literature on unplanted tanks says that establishing the nitrifying bacteria
>is a process that takes weeks. Why would a brand new planted tank have
>enough oxidizers?

Plants short circut NH4 and remove it. 
So the planted tank has little NH4 to begin with for the NH4=>NO2 bacteria.
They are not significant even if you added lots of NO3.

You can get around the substrate issue by doing this with only Riccia and no substrate also. 

> And why would they necessarily grow faster? Remember that
>at first you're starving bacteria that consume NH4, but heavily feeding
>bacteria that consume NO3 (if you're fertilizing a brand new tank, that is).
>So is it possible that denitrifying bacteria that consume NO3 could get a
>head start on nitrifying bacteria that consume NH4?

Denitrifyers live in a semi anaerobic environment(200-300mv), the nitrifyers like O2(400+mv).
NO3=>N2(gas) bacteria takes awhile to establish, certainly not an issue in a new tank 3-4weeks or less.

This arguement suggest that more NH4 will be produced in a older tank since it takes more time to establish a bacterial anaerobic layer, not the reverse.
NO3=>NH4 bacteria require specific conditions that are virtually opposite of a new tank.

>Robert, in your tanks what kind of NO3 concentration were you maintaining?
>When I bumped my NO3 level from 1 ppm to 10 ppm, it produced a measurable
>NH4 spike that lasted for days.
>- Jim Seidman

Okay, your test kit is likely off at 1ppm. The fraction of NO3 might be organically bound etc(non available to plants). Your plants were N limited/stunted, they were not removing any NO3 or NH4. NH4 built up, the plants took awhile to respond to the NH4/NO3. So the NH4 persisted for a few days afterwards then went away.

It was not the bacteria, it was N limitation or perhaps something else limiting the growth in conjuction.
Otherwise the plants will take up the NH4 first, not second.

I've never measured any NH4 in any new tank I've done.

Try this: remove the plants and add lots of NO3(say from 5 ppm to 25 ppm) and see if the NH4 builds and persist.
Then also see if much of NO3 is removed.

The tank should produce MORE NH4 if you are correct without the plants(which add O2 and remove NH4).

On a separate note:If the NO3 is removed via NO3=>N2 gas, you should see little NH4/NO2 and a decline in the NO3 level.
 
This is something a hobbyist can test themselves, no high tech stuff needed.

Regards, 
Tom Barr













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