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R: Strange Ph readings

Geroge Booth wrote:

>>>First consider any possible errors in reading the test kits.  What is
resolution of each kit?  If the pH kit is +/- 0.2 and the KH kit is +/- 0.5
the CO2 kit is +/- 3, consider the possible ranges of readings possible. 
numbers above are way off, so I don't think reading errors are the main

Note that other sources of alkalinity will make your KH test read too high.
pH of 6.5 and a CO2 of 10-15 mg/l indicates a KH of 1 to 2 degrees.  Have
done anything to alter alkalinity besides adding carbonates?  If the only 
buffering in the water is from sodium bicarbonate or calcium carbonate, the
kit will read true.  If you have added phosphate-based buffers, the KH test
NOT read true.  

Phosphate will also give false high readings with CO2 tests but you are
too low of a value based on pH and KH (CO2 should be about 38 mg/l for

Which of the values changed from when things were OK?<<<<<

Well it's hard to say wich is the value wich changed since last time.
When I did my last water change (weekly) I tried to lower my KH from 7 to 4
with a softer water but I didn''t know the exact value of the water I was
adding. So my KH reading could be right or could be wrong I will never know