Planted Tank Guru
Join Date: Jun 2004
Location: Baton Rouge, LA
Any drop checker is likely to give wildly false readings if you fill the bulb with aquarium water. And I believe that's what the ANS instructions tell you to use.
For accurate readings, you must use a solution of exactly 4 degrees carbonate hardness, commonly known as a 4DKH solution. I've seen them for sale on the Swap 'n Shop here, Ebay, various other places. Then add 2-3 drops from a standard pH test kit. Do NOT use the indicator included with the drop checker. In my experience, if it tells you to use tank water, the included indicator is usually faulty too.