Alkalinity Testing Issue

[willforr]

So I have two different ways I test alkalinity. I have an api and a RedSea kit to test it. API says my alk is at 7, but RedSea says it’s at 10?? I’ve tested them both more than once so which do I trust? By the way, I try to keep it at 10

 

[Auquanut]

I would tend to trust the Red Sea more myself. That's what I use. When I buy a new kit, I always test the new against the old, and they've always been pretty much spot on.

There is a margin of error with any test kit, but a 3 dKH disparity is pretty huge. You might try getting a Salifert kit and see what it says. Salifert is a pretty trusted brand and doesn't cost too much.

The most important thing is stability. Once you find a kit that you're reasonably comfortable is fairly accurate and very consistent, I'd stick with it. As long as it's close, I value consistency over accuracy.