Re: Bubbling plants

> From: jim kostich <jkos at execpc_com>
> Date: Mon, 24 Jun 1996 15:51:09 -0500 (CDT)
> But what do you think about my overall theory - that the "wonder
> water" was supersaturated with gases possibly of several types ...
> and that the sudden bubbling was caused by the inability of the water
> to dissolve any additional gases.

I would postulate that the Wonder Water is supersaturated with various
gases after it warmed to tank temperature from mains temperature.
Since CO2 is now in abundance (along with everything else), higher
levels of photosynthesis are achieved.  Since the water is already
supersaturated with O2, the pearling is the just additional O2 created
by photosynthesis.

> Another possibility along this line of thought is that the water might
> well continue dissolving O2, but be dumping some other gas
> simultaneously to "make room".

No, each gas has its own soluability (partial pressure).  One type
will not leave to make room for another.

> The above is all based on my assumption that the maximum solubility of
> each of the gases involved is limited by the presence of other gases
> already dissolved - an assumption which makes sense to me,

That is incorrect.  Many fish stores continue to advise against CO2
injection "because it will reduce the oxygen available to the fish".   
It just doesn't work that way.

> From: Stephen.Pushak at saudan_HAC.COM
> Date: Mon, 24 Jun 1996 18:40:30 PDT
>  I imagine that O2 passing out of the plant by this mechanism will be
> in solution rather than as gaseous bubbles.

True unless one of the vascular channels is exposed via a broken leaf
or stem. 

> When you observe O2 bubbles forming on plants and the other items in
> the aquarium, I believe that these are the result of oxygen diffusing
> out of solution at a site of chemical "instability". By that I mean,
> there is an electro-chemical reason for the oxygen to change states at
> that site just as rain drops and snow crystals require a tiny speck of
> dust to make the transition from a gas to a liquid or a solid.

I would call that a "mechanical" instability rather than electro- or
chemical.  The speck of dust is a discontinuity in the surrounding
homogenous environemnt that triggers the phase change.  Just like tiny
imperfections in champagne flutes give rise to streams of bubbles,
imperfections in the plant's surface provide sites for bubbles to
form.  Another example is that water can be supercooled to below
freezing under carefully controlled conditions but any disturbance
will allow it to crystalize.

> The ideal for your plants and fish is between 5-7 mg/L O2 (according
> to "Aquarium Plants Manual" by Scheurmann) 

More than 7 is bad somehow?  Oh, my poor discus <g>  This sounds like
unsubstantiated or outdated information to me.

> but this would only occur
> in a tank with clean water, strong light and few fish.

The water conditions and bioload don't matter as long as photosynthesis
is strong enough to generate more oxygen than is consumed.

George in Warm, Sunny and Just Perfect (for now) Colorado