George wrote:
"Sean Dinh" wrote in message
...

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 '__