how to read Ca test

[jedheuer]

Hi,

When I am testing Ca it seems that the color shifts from pink to purple over the course of say 5-7 drops. Do I measure my Ca levels from when the titration liquid starts to shift to purple or when it has shifted completely from pink to purple? It is quite a difference in Ca level.

Thanks.

 

[bertoni]

What is the brand of the test kit? Most kits turn blue at the endpoint, although the waiting time can be large.

 

[jedheuer]

Brand is Redsea.

 

[bertoni]

I've forgotten the specifics of that brand, but I'd go for the purer purple, I'm fairly sure. That's typical for calcium test kits. Be sure to swirl the tube for a few seconds or so between each drop. Are you using the standard test kit or the Pro version?

 

[jedheuer]

I am using the standard.

 

[bertoni]

Hmm, I'm surprised that there's that many drops involved in getting to pure purple. The resolution is only 50 ppm, if they haven't changed the kit. The Salifert test kit is much easier to use, in my experience, and the Instant Ocean isn't bad, although it does require a longer wait.

 

[Billybeau1]

I agree with Bertoni .

The Red Sea calcium kit is not very reliable from my testing. It'll drive you nuts.

Salifert and Elos have much better end points and are easier to distinguish.

 

[Percula9]

The endpoint for the red sea test is orange not purple.

 

[spleify]

<a href=showthread.php?s=&postid=14040800#post14040800 target=_blank>Originally posted</a> by bertoni
The Salifert test kit is much easier to use, in my experience, and the Instant Ocean isn't bad, although it does require a longer wait.

Not to try and hijack here, but I use the Salifert Ca test kits. I says the end point turns a clear blue. I always notice what the OP is saying, there is a point where it turns purple, and requires quite a few drops to get it to be clear blue. Now when you say there is a wait time. How long should I expect to have to wait to see a color shift? And when do I stop adding drops to get a color shift?

Thanks

Spleify

 

[jedheuer]

<a href=showthread.php?s=&postid=14041857#post14041857 target=_blank>Originally posted</a> by Percula9
The endpoint for the red sea test is orange not purple.

My bad, I am actually using the instant ocean. Sorry for the confusion. I think I will order a Salifert kit.

 

[bertoni]

The Instant Ocean kit worked for me, but I had to wait a full minute after the solution turned purple, and then continue the titration. The solution should turn a nice shade of pure blue, although they might have changed the test kit.