UG CO2 , UG flow measurements & Vermiculite

> From: Charles Bay <cbay at milton_ecte.uswc.uswest.com> wrote:
> Is CO2 injection into the substrate worth pursuing?

I think I'd discourage you from trying this. You could end up with a
strongly acidic substrate if the CO2 were being inducted into the
substrate at all. As well, you can't observe pH changes in the tank
quickly enough to control the amount of CO2 dumped under the substrate
and the result is an undamped oscillating feedback control loop. 
(translation: BAD pH swings)
> ------------------------------
> From: George Booth <booth at hpmtlgb1_lvld.hp.com>
> Date: Fri, 09 Jun 1995 08:36:34 -0600
> Subject: Convection currents [et al]
> I might even try this experiment.  I've got a spare 29g in the garage
> with UGF plates, a spare 5 amp transformer and I'm sure I can find
> some wire somewhere.
> Any suggestions on a series of steps?  UGF plate with no gravel first?
> Different heat densities? Karen Randall has done some work with small
> heaters in the uplift tubes to get a slow flow.  Any way of
> visualizing this flow with injectable dye or something?

Lacking sophisticated lab equipment, that is an excellent idea.
You want the dye in the centre of the tube. Anybody with a handy text
who remembers the integral to solve for this flow? There is a fudge
factor in the engineering text for laminar flow in tubes vs. the
velocity at the centre. You know the flow might be so slow that we
could only observe it after some minutes or hours. Hence no tank
turbulence or fish. Turn the heat up to max. The pressure will
be linear with temperature and at this low velocity, so will flow.
Also, the dye must not sink of its own accord.

Don't forget to do the second experiment where we time the level drop
on the same substrate with no heat so that we can tell what an appropriate
pressure head should be used for slow UGF experimenters! But then this
should be the same value as the difference in weight (density) of water 
over the thickness of the substrate at the ambient tank temperature and 
the local gravel temperature which was what +10 degrees or so?

  Pressure = (density temp 1 - density temp 2) x
             height of substrate layer (assuming constant temp thru it)
             / density of H2O (ave.)

By this we see that with a 5" substrate and a difference of .001 density
(I'm making up that number) the hydrostatic difference is .005 inches of
water!!! That ain't much and it's a lot smaller than that.

Re: Vermiculite

mica = Layer silicate clays forming small colloids in the soil with a
layered structure? Isn't clay an aluminum silicate too, just in powdered
form? The crystal structure of mica is arranged in flat layers
due to geological transformation by pressure. But thanks for the info;
I wondered where it came from! :-)

Jim suggested soaking Vermiculite in water and then squishing it to powder
and then covering it with a layer of sand or gravel to keep it in place.

I thought of the blender (but don't tell my wife I put mud in it! :-)

 - Steve