CYA test readings

[rmturner54]

I know this has been covered a million times and I have read almost every post on the subject. Since the readings are subjective at best I just got back in town. My wife been doing an amazing job with the pool and testing.
Her last CYA test was 60, 2 days ago. I tested this morning, bright full sun. At 60 and the dot starts disappearing, at 40 its no longer visible. What number should I go by?
Thanks,
Richard

 

[Abigail K]

Sounds like 40. You want the dot to completely disappear.
Also, it is best taken with back to sun (bright indirect sunlight).

 

[sangweb]

I am having the same debate so I decided to use my kids as 2nd opinion. I tested the CYA indoor and when I have doubt, I would ask the kids because sometime your concentrate on the dot stays on your brains even it is not there.

 

[jblizzle]

You should not do the test indoors. It should be outside in bright indirect light. Usually with the tube at your waist.

You can get the CYA standard solution from tftestkits.net which is 50ppm and then experiment with what light is right for you.