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Re: nutrient diffusion into vermiculite

Karen wrote:
> Charley,
> 
> > * Do you see a need for directly taking nutrients directly to the
> >   substrate to avoid high nutrient concentrations in the aquarium 
> >   water?  (High nutrients in water could force an algae bloom; the 
> >   substrate is low volume compared to the rest of the tank, and the
> >   principle of diffusion suggests nutrient concentrations in the
> >   substrate will merely achieve the same proportion as those
> >   concentrations in the water.  In short, can we get the nutrients
> >   in *sufficient quantities* where we need it, or *only* where we 
> >   need it?)
> 
> You overlook the fact that although many of our aquarium plants (like the 
> aforementioned Echinodorus<g>) feed directly from the substrate, many others 
>  feed direclty from the water column.  [snip]

Yes--I agree.  I guess I was *trying* to get to the point that in a typical
aquarium, the demand for nutrients in the substrate may be higher than that
demand in the water body.  You are right in stating that we don't want to
limit the plants we can keep (some plants are more dependant on extracting
nutrients from the water body instead of the substrate), and that floating
plants can be a good indicator of nutrient deficiencies in the water
column.

I have been doing some pretty extensive experimenting with floating plants
lately, and these things can be a pain <g>.  I get good growth, but they
won't stay put.  <bg>  I can still see me wanting to set up a tank largely 
without floating plants (or with plants primarily dependant on nutrients
in the substrate), and my concern is whether or not I can get nutrients 
into the substrate where I want it, and have the ability to minimize it 
in the water body (especially if it exists there already in 
sufficient quantities, but my roots are starving).  If I am dependant on
passive diffusion only, I have no such control at selecting the destination
of the substrate verses the water column.  Of course, adding it directly 
to the water body is trivial and should never be a limiting factor.  <g>

Maybe something blissfully simple is adequate:  No substrate circulation 
infrastructure, passive only.  Then, simply get one of those hollow rods 
for feeding plant roots in your yard (or merely a big syringe).  Inject 
nutrients into the substrate, and it will diffuse laterally (and no doubt 
some into the aquarium body).  We just have to make sure the concentrations 
are such that we don't burn the roots at the injection site.

--charley
charleyb at gr_hp.com	or	charley at agrostis_nrel.colostate.edu