Red Sea Calcium Test Kit Question

[Fringe09]

I dispense the titrator until it turns blue. If I wait about a minute or two, it starts to purplish. Is this normal?

 

[DLHDesign]

Yes. Titrate until you get to the matched color (or close - mine never get perfectly there), being sure to swirl it about the entire time. Often the last few drops will turn part of the test purple, but a gentle swirl will remove this color change. If you go a few more drops, the entire thing should turn and remain stable. Once you hit a stable color without swirling, read your measure.