Ca tests very different (salifert vs API)

[kevensquint]

Hello, I have a newish tank (about 3months old) that I dose the BRS recipe 1 kit to maintain Ca and Alk. The tank only has a few Montiporas and the corraline has recently started, so I've been raising the dosage of Ca and Alk equally. I have based my dosage on Alk and Ca test kits by API to try and maintain 8-9 DKH and 420ppm. Today I tried testing with the API and Salifert Ca kits and I'm confused. My API read 400 ppm and the Salifert 470 ppm of Ca. I tested twice and the same result. So, if I believe the API, I could raise the dosage a bit, if I believe Salifert, I should lower it a bit. API Alk test read 8 DKH and my Mg (salifert) is at 1350 ppm. What do you suggest ? Thanks for your time.

 

[bertoni]

Personally, I'd just assume the tank was doing fine, and let it go for a while longer. What is the resolution of the API test kit?

 

[kevensquint]

If I understand you right, its 20 ppm

 

[dixiedog]

Regardless which reading is right, you don't really need to raise or lower the Ca right away. You're in the acceptable range either way.

I'd just stay the course and see if I could get a third test done by a friend or LFS when I got around to it.

 

[bertoni]

Hmm, well, I'm not sure which kit I'd believe, but I agree that both values are acceptable.