Re: Just an Idea (plenum)

> From: zbigniew at netcom_com (Patrick Farley)
> [snip]  These us just an idea, no idea if it would work.
> Along with plants I'm interested in Reef aquaria also.  Friend of 
> mine jsut set up his reef tank using this substrate method which 
> optimizes the biological filter.
> It consists of multiple layers of different material.
> The bottom of the tank is empty, he placed empty cassette case on the 
> glass floor, on top of that he added egg crate, also known as light 
> diffusers for flourescent lights.   On top of that he add a layer of 
> screen door screen.  Then a layer of crushed coral, then two layers of 
> nylon screen, then a layer of finely crushed coral.

Yes--I've been reading on this "Jaubert plenum" (named after a guy named
Jaubert).  The "plenum" is the space below the substrate, with anaerobic 
denitrifying bacteria to help filter the reef system.

> What does this mean for plants...well.. How about the same thing with 
> different substrate.
> Use the light diffusers, first layer of screen, then a layer of laterite, 
> then a screen, or a layer of thick pebble/gravel, then several inches of 
> fine sand or small gravel.  
> My thought would be to run tubing down underneath the light diffusers to 
> force warm water or just a power head.   The water from this would be 
> from a sump.  In the sump you could either just add your fertilizer drops 
> or how about a laterite bed that you could replenish.  Use light 
> diffusers to make several layers and have water that would flow through a 
> bed of laterite that can easily be removed and replaced.  The water 
> (hopefully rich in iron) is pumped underneath the substrate and into the 
> laterite there.

I've been thinkning of something similar.  It solves one problem I can't:
You can pump heated water there, giving the effect of substrate heating
without heat coils.  However, my primary worry is that the water volume
I would send in there would be far too low to dose nutrients or keep the
temperature significantly different.  (I'm looking for slow circulation
through the substrate).  

You did get me thinking, though.  What if we had an in-line power head
down there?  Strong circulation in the plenum, but with a net pressure of
zero because it would only be moving the existing water (not forcing in
new water).  The power head's operation would heat the water in the plenum,
allowing for gentle convection up through the substrate from this
high-velocity, low pressure plenum.  Also, nutrients could be dosed:  Run
the airline tube from the power head out of the tank to a small cup, and
put a valve on the end.  For normal operation, the valve would be closed
and we merely circulate the water in the plenum.  Then, to dose nutrients,
simply open the valve and put 10 CCs or so of our nutrient addititives
in the cup, which the power head will siphon into the plenum, building up
positive pressure, and forcing some water from the plenum into the
substrate.  Then,

*  We can fully remove any anaerobic activity from the substrate.  At the
   first sign of anaerobic activity, simply open the valve and the plenum
   is "injected" with oxygen.

*  We can simply and scientifically measure the positive pressure in the
   plenum, and quantify/specify the rate of circulation through the 

*  We can directly (optimally?) add nutrients to the substrate without 
   high nutrient concentrations in the aquarium body.

*  We can have a very uniformly heated substrate without heating cables.

This is peer-review time.  :-)

cbay at gr_hp.com		or	charley at agrostis_nrel.colostate.edu