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Hey Y'all

I've got a paludarium that I set up in a 20 gallon high tank, oh some 5 or
6 years ago (envision some chin rubbing while I try to remember back
then).  I'd like to convert the paludarium to a planted tank and I'm
wondering if I can keep the same substrate. 

The substrate is a mix of potting soil, peat moss, Tex-Blast (sand
blasting grit) and a fairly coarse sealed aquarium gravel.  The stuff was
mixed so the result had the texture of a gravelly soil.  I originally
layered that about 8 inches thick and I kept just a couple inches of water
over it, with a little dry land at one end for good measure.  The idea was
to simulate a marshy littoral zone.  Over time the substrate has
consolidated to around 6-7 inches, most probably because some of the
original organic content has been mineralized.  I've also built a layer of
humic sludge in the deeper water by letting old duckweed and dropped
leaves remain in the tank where snails eventually had their way with it. 

The paludarium is on the lower rack of a two-tank stand.  The upper rack
held an aquarium with plant-hostile fish.  I used the paludarium as a
denitrifying filter for the aquarium.  A siphon dropped from the tank to
the paludarium and I pumped water from below a perforated plate below the
substrate back up to tank.  The siphon was controlled by a float valve and
the flow rate was clamped to a few gallons per hour with a ball valve on
the lift side.  The low flow rate and high organic content allows anoxic
conditions in the substrate.  Bubbles of odorless gas (presumably mostly
nitrogen) build up in the substrate and every couple months I have to poke
through it and release the gas because it breaks suction on the lift side. 

Originally the water that filtered through the paludarium was strongly
colored and I used activated carbon in an over-the-back filter to remove
the color from the aquarium.  It doesn't seem like the substrate produces
much color any more. 

I'd like to take out all but two or three inches of the substrate and then 
maybe layer an inch or so of mixed-size sand over the top to keep the 
organic particles out of the water, then fill and replant.

Can I expect this aged organic substrate to work well for a planted tank? 
I've read about high-organic substrates failing after a while.  Is the
layer of sand at the top necessary, or does the organic stuff tend to stay
down well enough to not worry about it?  Also, I use slow substrate
circulation with some success in one of my tanks and I'd like to continue
circulating water in this setup.  Does anyone have experience using
heating cables or very slow UGF or RUGF setups with a soil or organic
substrate?  If so, is water color a problem?  Are there problems that
wouldn't have come up in my paludarium that I can expect to see if I
convert it to an aquarium? 

Roger Miller
In Albuquerque where winter isn't quite done with us yet.