Drop Checker Help

After adding the 4dkh water to your drop checker, which pH regent do you use? I have an api master freshwater kit and I'm not sure which one to use, either the high range regent or the low range regent?

Use the low-range, from my experience I feel 3 drops to be enough for a nice royal blue color.

As for a source of 4kdh, I just purchase mine from greenleafaquarium.com when I'm purchasing other supplies.
 
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