Hi,
What are you using the pH test for ?
I have used pH test kits for a long time. Currently I use the high range pH test from Hagen. You can buy refills for the hagen kits for about $3. This test kit uses methyl. blue. They are relatively accurate (within 0.1). They don't suffer from calibration problems and Ag/AgCl reference degradation.
The pH is easier to read from a methyl. blue type test when less reagant is used (i.e. the colour is lighter so that you can tell the difference between green-blue and greener-blue).
BTW, I dialed in a calcium reactor with a test kit...same methyl blue kit.
- Victor.
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