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[APD] eH measurements

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.

Even a single data sample taken in an established tank would be quite

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, 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

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 but
that didn't bother the plants at all; their roots grew at the appropriate
depths. 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.

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. The idea
of a clay "cap" to prevent nutrient diffusion is a novel idea; I'm not
guaranteeing it would work mind you.

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

Steve P

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

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