Re: Dosing potassium with banana?

["James Purchase" <jppurchase at rogers_com>]

David wrote:
"It's wild-hair night tonight at Howell Park, and I'm considering
introducing potassium into the tank by feeding banana pieces to
the bottom-dwellers (or trying to...)."

Good God, man, you've got to get Cable! Playing with the remote control will
give you something to do with your hands.......lol

But, on a more serious note, feeding your bottom feeders small pieces of
banana is not likely to hurt them - the wider the variety of foods you
offer, the more likely it is that they will get all of the nutrients they
need to be healthy and live long lives. You might try alternating offering
banana with zucchini or peas.

Just make sure that you remove any uneaten portions promptly - don't let it
decay inside the tank, hoping that the potassium content of the banana is
going to find its way into your Hygrophilia. It might - eventually, but the
decomposition by-products that would be produced along the way are not all
that attractive. There are much easier ways to provide your plants with
Potassium.

Animals (like us) can get the minerals we need from our food and we can make
use of organic sources. Plants lack this ability - they only want inorganic
ions on their menu. Bacteria and fungi are largely responsible for
converting most minerals from one form to the other - the bacteria and fungi
attack organic detritus, consume it and convert the organic molecules into
inorganic ions. The wonders of Nature....

"In a related question, where does all the potassium that plants use
in the wild come from?  Certainly, it's "naturally occurring", but
what's the source?  (I suppose I should go find a freshwater ecology
book, huh? :)"

Try a book on Geochemistry as well.

According to Wetzel, who devoted les than a single page in Limnology (a book
which contains 1006 pages) to Potassium in fresh water, "Potassium is
actively assimilated into submersed plant tissues with a light dependent
exchange process of  recriprocal sodium efflux." (whatever THAT means....)
He continues, "Lake sediments are net sources of potassium during summer
stratification...".

Sounds to me like Potassium is actively and rapidly recycled in Nature. This
seems to be confirmed in a couple of Geochemistry texts I looked at.
Potassium is an Alkali Metal, with a valence of +1. When it is in rocks it
forms ionic bonds with the other minerals present. These ionic bonds are
relatively easy to break (i.e. the Potassium gives up the outer electron,
becoming K+). When rocks "weather", some of the Potassium in them (if they
do contain any in the first place) is dissolved out as K+ ions.

So, it looks like the Potassium in natural bodies of water gets there by
dissolving out of the rocks and soils in the vicinity. Once it is dissolved
in the water, it is readily absorbed by plants (algae and/or higher plants).
As plants die and decompose, either as leaf litter on the forest floor or as
detritus on the bottom of a lake, the Potassium contained in the dead leaves
is readily leached out and returned to solution, ready to be absorbed by
next season's plants.

Hopefully, any mistakes in this idea will be corrected by one of the
geologists on the list.

James Purchase
Toronto