[APD] RE: Fe and optimizing the substrate

["Thomas Barr" <tcbiii at earthlink_net>]

> Yeah, but I sure kept seeing improvement. In fact, the
> only way I could get Ammannia to stop stunting at the
> tips was to dose 6ml/6ml TMG/Flourish Fe, and then
> *good* color didn't really happen until 8-10ml's for
> each *daily*. I dosed before the lights came on. 

6mls of TMG and then just Fe for a 20 gal should be plenty, I had excellent
growth and coloration in this plant at much less even with plain sand,
RFUG's and no fish, 5mls 3-4 x a week TMG or Flourish.
I think many are Fe obsessed, rthere's a liot more to trace elements than
iron alone.
Adding more traces should be done with respect to biomass and uptake,
therefore, adding more traces should include all the traces, not just extra
iron.
The effects of adding or limiting certain trace nutrients has a more subtle
synergistic effect.

Seeing issues with say PO4, NO3, CO2 is easy and easy to detect, not so
with traces unless you do controlled runs, and when dealing with such small
amounts, metal cation chemistry, this becomes very very difficult.  

Adding more light will run you up against a wall in your _sources_ for
nutrients. You have to add traces at some point to the water column when
you keep adding light, CO2, NO3, PO4, K+ etc while a non CO2 tank will be
fine without any being added.

E.
> stellata constantly stalled, 

Mine has done well with higher macro levels. 
I have the same tank set up 20 gal, with Flourite and 110w/PC lighting.
I guess that tank has been up for about 7 years now. 
SeaChem Flourish is richer than TMG so the 5mls 3-4x a week should be
enough all on it's own.

and I couldn't get
> Rotalas (any species) to grow properly.

Mine do fine, Green indica, R macrandra, R najasen(sp), R wallichii, all
doing fine.

 I was unable
> to deliver Fe reliably no matter how much I dosed.

I'd do either two things, re-evaluate the macro routine, or I'd look to the
substrate then if the water column can no longer supply things.
If you do both, make sure the CO2 is 25-30ppm, better NO3 levels, 10ppm etc
vs 5ppm, good K+ 10+ppm, good PO4, I think you will not find so much
trouble and get more efficient usage out of the traces.

But many folks are very conservative with traces, much like PO4 in the past
and to some degree NO3 and much of the issues folks have can be exacerbated
by poor test kit readings etc.. 

> Further, the 8-9ppm NO3 that I added came right from
> the tap and that's all I needed. If I added even a
> couple ppm I had algae issues.

I've played with high NO3 levels in the past, your tank should not be that
sensitive to NO3 levels.
Something else is going on, tap water varies with respect to NO3 also, so
unless your testing often, that might be an issue also.
I've driven tanks up to 20-75ppm for 3 weeks at a time to see what might
happen, nothing happened.  
Many folks over dose with KNO3 when they start out using it.
I did. But I did not have anything except fear, no algae increase etc.

> Now that my substrate is set-up to properly reduce,
> and deliver Fe, I am able to dose WAY more NO3 (to
> good result), but I'm proceeding cautiously. 

Yes, you've found that the substrate MUST play a more active role in
supplying nutrients at high light levels. Hence my suggestions for flourite
etc in the past which will help lower light tanks also do better. There's
more play and variation at lower light and you can get away with more, but
at high light, the increased demands need to be met from both sources, iron
in particular, but perhaps more than simply iron(maybe Zn, Mn etc) and
perhaps there is a synergistic effect that includes iron also.   

I suspect
> the substrate is eating most of the NO3, though. 

I think the max rate I came up with in a non planted tank was around 1ppm a
day max from denitrification.
That is on the high side since if you add roots, less organic matter the
amount of denitification rates will go down as the higher O2 levels from
roots will raise the Redox levels out of range for good denitrification to
occur. 

There is a simple test to see this NO3=> N2 occur in anyone's planted tank.

Remove the plants and keep out in a tub/bucket etc for a 2-3 weeks or a
spare tank.
Leave the substrate in the tank, use a small tank such as ten gal or 5 gal
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 no#2
does and then week 3#.

I no
> longer need to dose PO4. Anyway, I find PO4 to be much
> less troublesome than NO3... 

Most do. PO4 limitation is not that bad as far as a plant effect, but
adding it will increase NO3 uptake.
If you want to apply the molar ratios, 8-9ppm of NO3 means roughly 0.6-0.8
ppm of PO4 to get the dry mass in aquatic macrophytes of 10N:1P. 

> The big issue for me previously(re: your remarks
> above) vs. your experience is that I was using plain
> gravel in a shallow bed. I'm sure you used
> Flourite/Onyx etc... 

Yep, I had the same damn issues, no matter how much I added, I knew I'd hit
wall and need to change the substrate or use a different apporach.
The light level that maxed out the sand and water column method was about
~4 w/gal of NO FL's. 
Beyond this, I had to take a different approach. 

>Except
> you, every hobbyist that I've spoken with has required
> WAY more Fe to be dosed in high light, HID/PC tanks,
> OR something special has be done otherwise.

Yes, the approach needs changed at this will mean better more robust stable
growth for folks with LESS lighting also, so everyone benefits.

 Enter
> various soils, humics, and homebrewed substrates.
> That's my angle on this whole topic.

I think we might be giving too much credit to lignite/peat/mulm etc
although they do play a start up role for the first few months and to get
the cycling going, I think most of the issue lays with the porousity of Eco
complete, Onyx sand, Flourite, Florabase, Turface etc and their iron and
trace content.

That porousity allows all traces to be reduced inside each internal grain,
not just iron.

To judge this effect, try a tank with RFUG, no laterite etc + high light.
Next try a tank with merely sand and lots of laterite + lots of light
Then see the difference when you add Flourite or Eco Complete

There are big differences between these.
If it were merely iron to roots, we'd see as good of growth with laterite
and yes, we see good growth, but not like these porous types of substrates
and this might be evident at lower light, but at 5.5 w/gal PC, you can see
this decernment. 

> NO3 is *easy* to deliver. Iron has some weird-isms,
> and plants get funny about it at high light. 

NO3 is tough to use but if nothing else is around, leaves or roots will
take this. Perhaps some reduction in the substrate will help, I'm not sure
till I fine a better method to add NO3/PO4 to the substrate, activated
carbon, Zeolite, lignite also hold promise for binding NH4/NO3.

Trace reductions and humics embedded inside grains will help in that area,
but if you build on each souyrce of nutrients step wise, adding both macros
and micro's, I think you will see the best gains. 

Substrate dosing like adding the jobes, can become popular and easy for
those who have trouble dosing routinely to the water column, even if the
water column dosing is EASY. Non CO2 tanks will also benefit from an
optimized substrate.

> >>The plant does not need that much Fe anyway.
> It's only one electron from Fe3+ to Fe2+.<<
>
> Yeah, that's what I can't figure out. Where the heck
> does it all go? Hehe... I *guess* it gets all bound up
> waiting to be reduced again? Turns to rust?

But it'll fall back into the substrate and be reduced again ultimately till
it's removed via plant biomass/prunings/complexes in water changes.

> Best wishes,
> John Wheeler

I think folks can learn a lot from the high light tank. It can be
frustrating, but you know the substrate's role MUST supply nutrients as you
increase lighting beyond a certain amount. The water column can be
optimized and still have issues with growth. But I think now we are on a
path to optimize the substrate more than Floruite or Eco complete can
__alone__.

Mulm and peat helped, Lignite may as well along with carbon/zeolite/barley
straw nuggets.
I think the next gain will be with Nitrogen additions and perhaps PO4
additions as well. 

But folks must be careful to closely monitor the NO3, PO4, CO2, K, GH
liquid traces in their water column to note real effects from the substrate
variables.
Test involving substrate interactions are notoriusly difficult. These take
time, often years and then you often left with speculation but a better
"hunce" hopefully.
Still, testing all that is a lot of work. I've done it for awhile to see
what I can learn, but after sometime it wears down.

Regards, 
Tom Barr



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