API Calcium Test kit

I currently use the API test kit, and it's really difficult to read..

The instructions say count the drops until it turns blue.

Can't really distinguish whether it's already blue or just dark purple.. :



What test kits do you use and recommend? And do all test kits have the same way of testing? Counting drops until it turns blue? Sorry, I've only tried the API so far.

 

They all use titration/color change method. I always do my tests in a room with bright lights to make the color change more obvious. I always add another drop after i think the color has changed to be certain. If it does not change then I know the previous drop was the correct count.

I use Seachem's calcium test it resolves to 5ppm.

 

Thanks for the reply.

I still have no source of a different test kit. The closest LFS here only sells API. But I'll look into Seachem, hopefully I'll find out.

 

IIRC, it should turn a deep purple. Neither in your picture is the color, it is unmistakable. How many drops did you add?

 

BTW, the endpoint color is about the color of the anthias head in my avatar. It turns pretty quick once it gets there, but usually takes a lot of drops for a reef tank (more than 20 is typical).

 

Indeed, it will turn purple like anthias's head in m2434's avatar. After that insutrctions say it will take only 1 or 2 more drops to turn blue. In your original photo, both vials are blue.

So if it took 18 drops to get to purple (anthias) and then 19th drop make it blue (your pic), 19 would be the final reading.