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Re: Reading Test Kits

Andy Moore wrote:

> Karen commented on my previous question:-
> "Do you really think that in absolute terms it matters whether or not you
> can read the difference between .1 ppm and .2 ppm in your test kit?  "
> Matters to me !  Probably doesn`t make any difference in absolute terms

Maybe you should rethink your concerns.  The APD places a lot of emphasis
on using test kits and I think that emphasis might be a detriment to our
ability to care for our tanks.

Water from my aquariums regularly pegs the scale on phosphorus test kits -
or seems to peg the scale, anyway.  The color produced never quite matches
the color in the charts.  It's greenish when it should be a fairly pure

Just the same those reading led me on long and repeated searches for
ways to reduce phosphate in my tanks, none of which (according to
the test kits) actually worked.  Also, none of them had an evident effect
on plant or algae in the tanks.

Then it turned out that the greenish hue in the test results probably
meant that the test response was caused by the silica in my tap water, not
just by phosphate.  Judging from the response of my tanks to the addition
of phosphate-containing fertilizer the tanks are phosphate-limited and
they probably have been for quite a while.

If I watched my tanks instead of my test kit, I might have known that long

> "Do you have an algae problem? "
> Yes !

While browsing last night I found out that algae (at least some of them)
have phosphatase activity.  That means that they can salvage phosphorus
from organic molecules.  Our test kits read phosphate, not total
phosphorus (which would include the organic phosphorus) so it's quite
possible to have little or no phosphate in your test results and still
have algae thriving happily in your tanks.

> I can`t really see the point of buying a test kit if it is difficult to
> read - perhaps I should change to eg. LaMotte like my Fe kit. I`m not quite
> as experienced as you Karen at looking at the plants and guessing what may
> be wrong with them.

I can't really see the point to buying a test kit if it doesn't tell you
what you need to know.

Roger Miller