"David Marshburn" wrote in message
...
SLEngst wrote:
: K is the symbol for the element potassium.

and, as an adjunct to this, is it in fact turbidity that is the measure of
potassium in water? i always wondered what turbidity was. are there
other factors contributing to turbidity?

I believe that there was a post a few days ago that contained a comment
about using a turbidity test to determine the level of Potassium in a tank -
this might be the source of your confusion.

Potassium is difficult to test for. Chemical methods designed to "snag" the
Potassium in order to quantify it in a test tend to also "snag" other ions
in the water as well, and it is difficult to isolate the K from the
interference. The only chemical method which is adaptable to hobbyist level
test kits uses the turbidity of the sample (after reagent chemicals have
been added to it) as a measure of the level of K. This isn't the same thing
as the turbidity (cloudiness) of the water in your aquarium. Turbidity tests
can be very difficult to read - they depend upon having a good eye and
knowing how to compare a sample with a standard. If you have the money, you
can buy more sensitive electronic testers for it but they are not really
necessary for hobbyist purposes. Potassium is a macronutrient, needed by
plants in relatively large amounts. It does not appear to have adverse
effects over quite a wide range of concentrations. I have only ever heard of
one instance of an excess of K causing problems and I believe that the
levels in that case were in the order of 10X "normal". Anything in the 10-30
ppm range ought to be O.K., with the upper end of the range being more
appropriate in extremely high light, CO2 enriched tanks.

James Purchase
Toronto