Red Sea KH test off by.... 2.5 dKH?!

[capt_alaver]

I'm pretty surprised at how inaccurate the KH test in my Foundation Pro kit is. I got it from BRS and its expiration date is 12/23.

My friend got the Hannah Marine Master for a build he's working on. He brought it over here so we could mess around with the thing and figure out its quirks.

The HMM read my alkalinity at 10.7 dKH. My KH test read 8.2 dKH which is what I tuned my dosers to... twice. We retested using freshly mixed Red Sea saltwater from my LFS as a "control" of sorts. The HMM read 8.0 dKH which matches what they advertises, but my Red Sea kit turned at 6.2 dKH.

The Calcium and Magnesium tests in the kit were pretty inline with the HMM's results, but it's just so surprising to see the KH test missing the mark by such a huge margin - especially considering how important that nutrient is to maintain.

I know 10.7 isn't high and it was kept pretty consistent. But my dumb self has been doing 50% water changes every few weeks with water that has waaaay lower KH than my tankwater. I guess that's on me for not testing both or verifying the accuracy of my test kit. Corals don't look upset, thankfully, but now that I know, hopefully they'll start to look even better.

 

[Drewe]

While being off 2.5dKh is definitely a lot...

If the test is consistently off in the same direction, and you perform it the same way each time, and everything is happy? I'd let it ride and continue doing what I'm doing. If you want to raise or lower Alk just adjust your priors when dosing.

The best test is the one you do the same way each time. That's why most people use the Hanna checker for Alk. It's almost impossible to do it inconsistently and there's no ambiguity in the results.

 

[capt_alaver]

Yeah, it's hard to do the KH test differently. I'm just surprised that it was consistently so far off base. I'm also upset at myself for not checking the saltwater and doing such big WC's with a ~2.5 dKH difference between the two.

 

[homer1475]

As stated, sure your doing the test correctly?

When I first got a hanna I cross referenced it with a salifert and red sea pro for a while as I did not trust the hanna, both were well within specs of the hanna, and continues to run consistently between the 3.

The easiest test is to test your freshly mixed water. They should be fairly close to each other, but will not match exactly(margin of error between the 2).

 

[Randy Holmes-Farley]

I don't now which one is off, but one always needs to be suspect of hobby devices.

IMO, that 's one reason to do alk diy:

A DIY Alkalinity Test: By Randy Holmes-Farley - REEFEDITION