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Re: NO3/NH4/PO4

This is not a bad thread to follow.

> No fishes. No food. Today I just bought 2 Oto's and 2 Epalzo's. Algae
> eaters ,as you suggested, so still no food added.


Well your going to use more KNO3 then. You can do it this way if you wish
but it's better to have fish in the tank for a number of reasons. The whole
attacks the algae is a good enough one all by itself but perhaps the most
popular reason is the NH4+ they produce which will reduce the amount of NO3
taken in some(you want a source of both NO3 and NH4, but only tiny amounts
of NH4 which is best added via the fish). If you add too many fish you get
too much NH4 -> algae bloom. There a range of fish bioload you can have but
generally I go fairly low stocking levels. If you go higher, try using a
wet/dry filter since it can convert the NH4 to NO3 faster if the plants
cannot manage to take up all the NH4 before activating the algae to respond
to the NH4. Folks have said that filterless tanks are great since the
bacteria don't use up the NH4. Well that a sensitive balance to maintain and
a bit too dicey for most folks. Okay in small tanks. Current seems to help
plants a great amount. Better to err on too much filtration. But a large
amount of the NH4 uptake is in the gravel layers(lots of bacteria there),
not just the filter. So this becomes an argument over a small amount of
bacteria in the filter. I've seen far worse responses from a substrate being
disturbed than any filter.
  
 
> yes. They are from ADAŽ. They add traces and iron separately but if you
> look at the params I gave you in the URL, you will see that there is almost
> no iron, as I'm adding traces.

Add both. Tweak this later though. For now add more iron(2x a week). Don't
worry that it will go to 0.00ppm for a few days(2 or so).
 
> yeah! Really amazingly fast! But now the point is: PO4 is uptaken(or else
> where? filter? substrate?) pretty fast.

Well the substrate get saturated at some point if you have iron in there.
Filter usage, fish uptake etc can be assumed to be negligible. So all your
left with is plant and algae uptake. No algae then-> all plant uptake.
Assumptions are important when considering what is happening in your tank.

> So I read 0 ppm, but when do plants
> will need it again?

In a day or two. You cannot see PO4 deficiency well IMO. But your tank has
it. I add as I see the levels fall below .4ppm. The data I had suggested
that plants uptake about .2ppm a day in my takes on average over 10 weeks
worth of runs. Started at 1.0ppm and by week's end(7 days) I had 0.0ppm.
That was with fish too. So it's probably a higher rate in a well run tank.
NO3/CO2 are the biggest issues for most folks though. Nothing goes right if
you louse those up.

 is it better to maintain a concentration in the column
> water above 0ppm *costantly*? or is it better to give a burst?


Well, I think it's better to have a residual(since the plants are arguably
taking it in), but you can get good results with pulses 2 x a week also.
Try A and then try B:) Then you decide.

> the 2nd idea sounds better to me cuz plants are not good scavenger as
> algae, 

I do not agree. If this were true, which it isn't in this context, I'd have
algae all over my tanks. But I do not(and many others), so some other
interaction/mechanism must be working. I have less algae growth at higher
PO4 valves(at least up to 1.5ppm -1.8ppm) and better plant growth. Again,
you try and see for yourself. Proved it to yourself.

> and after all uptake is against concentration, plus plants store
> much more tha algae. what do you think?

I'm certain algae can survive at much lower PO4 concentrations than any
plant. Algae also can produce gametes easily(resting zoospore/zygospores)
which can wait for long period till things are ripe for growth(algae...
"seeds" if you will). Assuming uptake is based on concentration is a *good*
assumption for uptake rate. But the plants are growing pretty fast and
producing large amounts of bio-mass compared to the algae.

> today I have a devil idea:

Stay away from him.

> I added NH4 instead of NO; 0.24ppm NH4. Why? I
> thought that NH4 uptake is faster than NO3 and so N supply will stay
> shorter in column water than NO3. It was uptaken in 1 hour or so!!! NO3
> then is a measure of what/how much Nh4 is uptaken cuz the rest will be
> converted in NO3 by bacteria, so if the NO3 level stay constant, I'm adding
> the proper amount of NH4. NH4 tonight 0.00ppm and NO3 was 1ppm.

Careful since if you add too much NH4 you will get algae. Or dead fish if it
gets too high. This is were you want to use the small "pulses" but a better
solution that will greatly enhance the tank is to simply add more fish which
will be far safer. But the rate of uptake does not surprise me.
 
> I'm aware of these processes. Generally I'm trying to keep very low values
> of all the organics, monitoring the COD. And I put a lot of activated
> carbon in filter canister, so it *should* be okay.

Wait a minute, Carbon? Now ask yourself if carbon will remove NH4?
Regards, 
Tom Barr
 
> ciao,
> Luca