Observations on a high organic substrate

In a previous submission I had described production of ammonia
from an experimental substrate in a 50 gallon tank using a
250 watt Metal Halide pendant and CO2 injection.

My substrate which has almost 50% humic matter in the
middle 1" layer has been growing plants quite well. Some plants
(H poly) which I trimmed did not recover as well as usual. I
theorize that the removal of leaves affected the plants ability
to protect its roots by providing oxygen and the roots had
to suffer a set back. Some of the plants took a long time
getting established in this rich substrate. Initially I attributed
this to a set back after the bleach treatment.

I expect the substrate is too anoxic. 50% organic material in 
the middle layer of the substrate is too high even though this 
organic material is primarily humus.  There was still a high 
nutrient content. Hopefully the substrate will stabilize as the 
free nitrates are consumed. The remaining organic material should 
be fairly resistant to further decomposition.

The substrate seems to have ceased producing large amounts
of gas bubbles this week.

There was .25 ppm ammonia about a week ago so I started
a biological filter. The Crypts love this anoxic soil and are
growing gang busters as does Alternanthera. I wouldn't repeat
a substrate this organic again. For the next I will mix more
Fe rich clay into the organic layer.

Interestingly, the roots of the Crypts have the same thin
coating which I described in another posting. I theorized that
this layering was a result of a profusion of root hairs designed
to provide an oxygen rich boundary to protect the roots in an
anoxic environment. Has anyone else observed this type of
clay coating on Cryptocoryne roots? What causes it?

Steve Pushak
Vancouver BC