Re: [Killietalk] Nitrogen, nitrate, nitrite and ammonia

[Barry Cooper <bjc3 at centurytel_net>]

I can't answer the question about the speed of uptake of nitrogenous 
compounds by plants, but of course it would depend on the density of 
plants. I would not depend on plants to take up ammonia. If you had very 
actively growing java moss in the tanks they will be taking up 
significant quantities of nitrates. Periodically having to remove excess 
java moss is a way to remove nitrates from the system, but I think water 
changes are more dependable, and they remove other wastes too. We don't 
want to kid ourselves that nitrates are the only waste products that 
build up in aquaria.

One of our chemists will probably explain this better than me, but gases 
dissolve in water according to their inherent solubility and 
proportionally to their partial pressures in the atmosphere at the 
surface of the water (that is, their relative proportions). CO2 is much 
more soluble in water than oxygen is. In a CO2 injected system you are 
increasing the atmospheric CO2 partial pressure, but not to massive 
levels. There are still other gases, including oxygen. In fact, in such 
a system, plants will "pearl" giving off oxygen. Sometimes streams of 
oxygen bubbles can be seen coming off plant leaves. Thus you are also 
increasing atmospheric oxygen levels at the water surface and therefore 
increasing oxygen content of the water. All this assumes, of course, a 
covered tank. It wouldn't be very useful to add CO2 to an open system. 
People make a big deal about producing tiny CO2 bubbles to get the gas 
to dissolve, but most of the dissolution occurs at the water surface. 
Similarly, in an open system, much of the dissolved CO2 would escape at 
the surface.

Barry

Barry J. Cooper
Sweet Home, OR 97386



Rusty Scalf wrote:

> I have two questions:
>
> > Hydration and hydrolysis  and ionization and free reactive molecules 
> > would answer your questions Wright, along with life form specific 
> > susceptibilities. So we need ionization constants, dissociation 
> > constants along with susceptibility to explain all this water chemistry.
>
>
> What is the speed with which plants take up all these nitrogen 
> compounds? I imagined that nitrates and ammonia in solution would be 
> actively transported into plant tissues upon contact. Java moss should 
> act as a nitrogen vacuum cleaner, no?
>
> > How can we explain so many fish doing well in CO2 saturated water? 
> > The plants seem thrive in it But don't the fish need O2?
>
>
> Per the carrying capacity of water, what is the relationship between 
> O2 and CO2?  Is it one of competitive exclusion?
>
> Given what the plant people do to their tanks with CO2 injection,  a 
> competitve exclusion scenario would kill fish pretty quickly I would 
> think; Especially given the higher solubility constant for CO2.
>
>     Rusty Scalf
>
>
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