[APD] Substrates

[Thomas Barr <tcbiii at yahoo_com>]

 "What I would be most interested in learning in the planted aquarium would be
the eH at the bottom of a soil+peat substrate approximately 3" deep. I'm not
at all concerned about the profile of eH with depth; we know it will vary
continuously in between the level at (or near) the bottom and the level of
well-oxygenated water at the surface."
 
I an predict it, I'd say about 200mv depending on grain size and organic matter content. 

"Even a single data sample taken in an established tank would be quite
useful."
 
For what? 

"Ideally it would be nice to set up a fresh aquarium and take measurements
weekly for about 2 months & then monthly for about 6 months. In order to
test the assertion that eH increases with age in a planted substrate that
has become root bound,"
 
Well that's not what's going to lower Eh, organic material addition will almost always lower Eh. Healthy active roots will raise Eh.
 
I don't think you will gain much by looking at the depth layers or some semi standard depth/peat mix etc.There's too much variabilty and other competing interactions going on. 
 
" you might have to wait a couple of years for the
progression of a Crypt colony to become that established. If you used Bacopa
instead, it would not take nearly so long. Paul once told me that Bacopa is
able to convey a lot of oxygen into the substrate and it grows quite
quickly."
 
Yes, that's true. There are many spcies you can try but I reaslly am not certain what the question is that you hope to answer by going to all this trouble. 

"The largest specimens that I ever grew came from my large cube tank with a
10" deep substrate. I was using a soil & sand mixture with clay fertilizer
balls. I know that the eH was low enough to produce sulphurous smells"
 
So that would be about 0 to -100mv range. 
Fe reduction at about 100-200, Mn about 150-200mv to 250-300mv or so and NO3 at 300mv range.   
 
"but
that didn't bother the plants at all; their roots grew at the appropriate
depths."
 
Well, of course, but the __root zone__ is NOT that reduced. The root will not live long otherwise if it cannot get O2 down there. 
 
" I did not find roots at the bottom of the aquarium but perhaps I
would have if the tank had stayed active for more years. I had to move to
this present location about 5 years ago & I used pottery containers
exclusively in that tank. The C blassii has never achieved its previous
glory and has continued to shrink as the container has become more crowded,
even with thinning."
 
C cordata var blassii is a weed. But if left alone it will do wonderful in rock hard or soft waters. The best plants I had were raised in 6 inches of Flourite, tons of CO2, lower light 1.6 gpw, triton/cool white mix, rock hard tap water, weekly dosings of NPK traces, weekly 50% water changes and a moderately to high fish load. 

"I think the biggest problem with using a "rich" mixture is necessarily the
low redox (eH) but the problem of nutrient leaching into the water."
 
Well low Eh will produce nutrients like Fe2+, NH4+, PO4 and if those leach out, it can cause issues.
 
This is one reason I have always talked about CO2 being higher than you think you need.
Plants will gobble these up fast if they enough CO2.  
 
 "The idea
of a clay "cap" to prevent nutrient diffusion is a novel idea; I'm not
guaranteeing it would work mind you."
 
Well, if you plan on not replanting/uprooting ever.

"My point is that low eH is not really that harmful to plants.

Steve P"
 
I agree, but the plants mediate their environment with O2 transport to their roots anyhow. 
The nutrients are not harmful but.......... H2S is harmful to plant roots and not a good thing.
 
You need a balance of organic matter, but too much.
 
The mulm method works well and a little peat does also.
It's not a precise thing, I doubt it ever will be, but a generally under shooting seems better for this than adding too much.
 
Light will play a big role as will adding CO2 gas/Excel etc.
As you add more light and CO2, the less dependent the tank becomes on the substrate and the more dependt it becomes on the water column to mee the nutritional needs of the plants.
 
This why a non CO2 soil tank with less light works great for long periods without much maintenace etc fish feeding(fish waste= small amounts of plant food), water changes etc.
   
But you can get great health and slow growth by adding CO2 to a low light tank.
 
I think this yields the best combination.
 
Flourite is nice because each grain is a porous microsite that has an aerobic outter layer and an anaerobic internal layer on EACH grain. Then all that layering with sand, clays, peat, dirt etc really is not needed, the degree of organic matter can be less to get the same ranges of Eh's. You can also pull up roots and replant without any issues to speak of.
 
Regards, 
Tom Barr

"P.S. Thomas, please consider this sent directly to you but incidentally CC'd
to the APD"

 
----Careful there, I'll sue you in Federal court and report you to the FBI for computer crimes. 
 
 

 




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