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Re: KH and hair algae, valisneria

Perhaps one of our botanists can help correct a possible misconception that
may be sprouting here (or another one I may have been laboring under lo
these many years). 

It is my impression that bicarbonates (HCO3-) and carbonates (CO3--)
contribute nothing directly to plant growth. These are not considered macro
or trace elements that are needed for plant nutrition. Perhaps certain
plants that have adapted to harsh environments can extract needed carbon
from them in the absence of dissolved CO2, but they are not directly needed
for plant growth if CO2 is available. 

This implies that bicarbonates and carbonates are not "used up" by plants
under normal growth conditions. This also implies that bicarbonates and
carbonates do not need to be replenished on a regular basis unless
something else is using them (for example, bicarbonates combine with the
free H+ ions generated during nitrification). 

To me, bicarbonates and carbonates (I like to call them "KH" just to annoy
the scientists reading APD :-) are useful solely to provide buffering and
to achieve specific ph/CO2 relationships. A certain amount of KH is NOT
needed by plants for any direct reason. A certain amount of KH conbined
with a certain amount of CO2 will produce a favorable pH. That is the only
thing KH is good for, IMHO. 

Some plant books (Baench Atlases specifically) describe plants as requiring
certain amounts of KH and don't mention GH. I wonder if this is a mistake
in translation or an author's misconception or if I'm off the deep end. 
George Booth, Ft. Collins, Colorado (booth at frii_com)
  Back on-line! New URL! Slightly new look! Same good data!