"Elaine T" wrote in message
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George wrote:
"Elaine T" wrote in message
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George wrote:

"Sean Dinh" wrote in message
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TT and nitrate reduction...
http://tinyurl.com/4hlhx


10 ppm is not acceptable in reef aquariums, and I strongly suspect it does
little good in large freshwater systems (such as garden ponds) with
no/inadequate plants to remove it. Hence, the algae blooms. In a sand bed
that uses a Jaubert plenum, a porous plenum is constructed beneath the bed
with a void space below the bed that is filled with water, anaerobic
bacteria form in the bottom depths of the substrate and in the water below.
As anaerobic bacteria cultivate, they remove nitrates. Anaerobic action
produces a fair amount of heat. The heat warms the water layer below the
gravel. The warmer water flows upwards, displacing cooler water above the
gravel. This action moves water through the plenum at very slow rates. The
slow movement of water through the gravel helps to prevent dangerous
hydrogen-sulfide gases from forming in the plenum. The deep gravel bed also
provides a home for burrowing motile invertebrates which feed on solid
organic mulm and detritus. The idea here is to move away from systems that
required heavy maintenance to prevent nitraqtes from getting too high.
Trickle filters work great in removing nitrogen compounds over a limited
time period before they must be maintained (i.e., cleaning pre-filters,
etc). Sand beds with a Jaubert plenum usually never have to be cleaned
because, if it is properly constructed, there is no build up.

http://www.practicalfishkeeping.co.u...?article_id=21

Jaubert plenums have been tried in large FW planted tanks shortly after they
became popular in sal****er. It is much harder to get a population of
denitrifying bacteria in FW that does not include sulfur reducing bacteria
and generally attempts at denitrification in FW crash and burn. Sulfur
reducing bacteria establish in the plenum, poison the water, and fish start
showing all sorts of bizarre diseases in what otherwise seems to be a healthy
system.

--
__ Elaine T __
__' http://eethomp.com/fish.html '__


Do you have a link to any papers on this? I found a web site this evening
that describes the set up and it seems to suggest that it works very well, at
least in freshwater aquariums. It also recommended to use 2-3 mm diameter
gravel instead of sand. Since we are talking about a lot more water, I am
considering using even larger gravel (probably something slightly smaller
than peah gravel). I've also read elsewhere that fears of crashing and
burning are unfounded if it is done properly. Of course, like any
experiment, I'll have to monitor it. Sulphur-reducing bacteria could become a
problem if the substrate becomes completely anoxic. But most sulpur-reducing
bacteria are anoxic. The idea of using a live gravel bed in a garden pond
must take into considerations all of the needs of the bateria that will live
there. De-nitrifying bacteria are anoxic, while ammonia reducing and
nitrite-reducing bacteria are aerobic. The idea is to get all three types
growing in the same substrate. So can we expect these three bacteria to live
viably together? The answer is yes, IF oxygentated water is induced to flow
just above the gravel (parallel to it), which will induce flow/exchange
within the gravel, but at a low rate. I suspect that my hogs (fish) will
also root around in it enough looking for food that it will get enough
oxygenation. But I plan to come up with a way to create the current flow a
few inches above the gravel. I already have a very thin layer of gravel on
the bottom (I had extra gravel when I built my biofilter, and I wanted to add
a little color to the bottom of the pond), and they do root around in what I
already have there. But I will certainly take your advice at heart before I
make any final decisions. Thanks for the advice. Oh, and after reading that
article, and your advice, I will probably lose the plenum and just build the
substrate right on the bottom. Here is the link to the site I found:

http://www.athiel.com/lib/lg-fw.html

Here is another one about gravel filtration (as opposed to undergravel
filtration):

http://www.athiel.com/lib/ugfilterarticle.htm

Just read the part about gravel filtration.
I can't find the failed Jaubert attempt right off, but here's some on similar
denitrification attempts - not formal, and nobody as famous as Thiel.

http://www.thekrib.com/Filters/plenum.html has an article on the shortcomings
of Jaubert's original idea in FW.

http://www.thekrib.com/Chemistry/nitrate.html has my own account of trying to
use a commercial denitrator called a Nitrex box. It was a flat, black box
with a nutrient mix for denitrifying bacteria that was supposed to prevent the
growth of sulfur-reducing bacteria. There were slots for convective
circulation and you buried it in the gravel to form something like a plenum.
I got nice denitrification for a while and then the typical H2S crash and
burn.

http://www.thekrib.com/Filters/denitrator.html has George Booth's DIY coil
denitrator design. Similar to my experience, after a few months of successful
operation, the coil started pumping H2S into the tank and killing fish.
George Booth is a gifted plant tank aquarist, and if anyone could have pulled
off denitrification it would be him.

I was reading rec.aquaria avidly then and nobody managed a successful
denitrator design in FW other than bog filters or algae scrubbers.

However, Thiel's live gravel article is very interesting. It's actually quite
easy to run a planted aquarium with only water movement and minimal
filtration - the so-called Dutch Aquarium. The plants and gravel provide
plenty of surface area for filtration. Malaysian trumpet snails (alas,
tropicals) provide substrate turnover, with a loach keeping the population
from getting out of hand, and the plant roots prevent anaerobic zones from
developing.

Doing this in a pond seems possible if your fish...er hogs stir the gravel and
circulation over the gravel bed is good. I wonder if there is a coldwater
snail that would burrow in the gravel to help things stay aerobic? I'm sure
you'll get plenty of healthy nitrification in the least. I hope it works out
with some denitrification as well.

--
__ Elaine T __
__' http://eethomp.com/fish.html '__

I am looking into what critters I can expect that might populated it
"naturally", and what I can introduce. I don't plan to plant any plants in the
substrate (it will be 45" below the water surface, at any rate).