Re: Indicators

["S. Hieber" <shieber at yahoo_com>]

Rachel asked:

> I am pretty much dosing according to Tom Barr's
> recommendations. The only 
> nutrient test kit I own is NO3. Is it reasonable to
> assume that if N levels 
> are correct, the other nutrients in the tank are also
> correct?

Yes, in the same way it is reasonable to assume that if the
water level in one tank is on target, then the water levels
in all your tanks are on target.  Well, that's not a great
parallelism so let me explain.

If you're controlling nutrient levels with dosing and water
changes and everything is working, then KNO3 levels, or
even the plant performance, might be a good indicator.  But
if other factors can be involved, like fish food, then, for
one example, PO4 can be out of whack while the KNO3 is
entirely within whack.  My occasional BGA outbursts, which
usually precede one of my swearing outbursts, insist that
this is the case.  But using BGA as an indicator is
Draconian method, best employed when not needed ;-) .

When I get everything stable (plants show it, lack of algae
shows it), and I'm following Tom's guidelines, I find that
the test measurements keep coming out the same, week after
week.  So then I start to do tests less often.  In fact,
and here is the kicker, I mostly just do the KNO3 test to
see if overall dosing is tending to drift high or low --
like maybe my plants have grown so much that they're
sucking the nutrients out of the water much faster.  I find
the KNO3 test much easier to do and read than the PO4 test,
so I use that.  Vice versa seems just as valid.

Likewise, if my tanks are all stable and under the same
regimen and conditions, and I see that the water level is
okay in any one of them, then I know it is okay in all of
them.  That is, until or unless something changes the
regimen or the conditions.  ;-)

Scott H.

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