Red sea calcium test blue turns back pink

[Dondante]

So I use a magnetic stirrer. When I drop and it finally turns blue it turns back to pink after a few seconds. Is this my mark or should I keep dropping until it stays blue?

 

[saltyhog]

Your mark should be when it remains blue. What you're observing is a good indicator that you are getting close to the end of the titration.

 

[Reefs and Geeks]

Not sure about the red sea kit, but many titration type tests will start to change color but go back when you are getting close to the endpoint. This is because the titrant is more concentrated in some parts of the sample and is strong enough to reach the endpoint there, but once it's mixed more the homogeneous sample isn't quite there. Unless someone has more insight specifically into the red sea test kit, I'd go with the point that it stays blue after mixing. chances are you're only a drip or 2 away from the true endpoint.