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RE: Lamotte O2 test

John asked:

"I inject O2 and also inject C02.  I have a Lamotte Oxygen test kit and
recently got a reading of 9 on the tritation scale.  The scale on the
tritation tube goes from 0-10.  The problem is that I don't know if '9' is
a good number or not.  Can anyone tell me what acceptable readings would be
using this test kit?"

The reading that you get on the titration tube can be read directly as ppm
and there are 5 divisions between each number, so it can read to 0.2 ppm
over the range of 0 - 10 ppm. According to a post made a few years ago and
archived on the KIRB, the saturation point of O2 in freshwater of 80F is
approximately 8.1 ppm at sea level. At higher elevations and at higher
temperatures, it would be less.

It is possible to super-saturate your water with O2, but I don't know if
this is what is happening in your tank. The instructions that come with the
LaMotte Dissolved Oxygen Test Kit are pretty clear and straight forward but
conducting the test itself can be tricky - you may just have overshot the
titration point.... it only takes a drop or two for the reading to be "off".
The actual disapearance of the "pink" color (which signifies the endpoint of
the titration) can easily be missed unless the vial is viewed in the proper
(white) light and against a pure white background. This applies for ALL
titration tests.

How (and WHY) are you injecting O2 into your tank? A well planted, properly
maintained aquarium should have no problems with lack of Oxygen without
going to the bother of us having to "inject" it.

James Purchase