API Calcium Test

I'm unhappy with my API calcium test. I've only been using API for Ca and have been using Salifert for everything else. I had no issues with API Ca up to now. The Ca test was nice since a color chart isn't involved. You simply count drops until the solution changes from pink to blue.

When I bought this last test kit I noticed that my Ca had dropped quite a bit. I didn't think much about it because I hadn't tested for a week or two but thought my Ca had dropped kind of quickly. In time I forgot about this until I started having problems. I went out and bought another API Ca test and compared the results. My older kit was measuring 420 ppm and my brand new one was measuring 520 ppm. Which one was right?

Neither...

After I found out I couldn't trust my API test I bought a Salifert Ca test. It measured 480 ppm. Essentially right in between the two APIs.

The APIs are now officially tossed in the trash. I'm using Salifert for everything now.