Thank you. I will try that. I had almost every test kit you can get in api. Then I heard Hanna is supposed to be more accurate so I bought them, and boy was my wife mad when she found out how much they were, but I keep getting what I believe are incorrect readings. Also where do I find the video your talking aboutFor what its worth. I am using the Hanna Calcium checker. One thing I have learned is the cuvette need to be spotless. the other is, when putting the cuvette in the checker, make sure you put them in the same way when doing the C1 and C2 check. What I mean is, on the cuvette there is a white ring around the top or fill line marked 10ml on one side and on the other side it is blank between the ring. If you put the 10ml into the checker to zero out (C1) facing you, put it back in the checker the same way for your C2 reading. If you put in a different way, it may pick up blemishes or glass imperfections when the light shines through during the C2 reading and may throw off the reading.
Definitely watch the videos which may help.