KHD Readings were too high - now too low

Hello - I am new to all this so please forgive me ;)

I bought the KHD Standalone on the 6th - spent the day and night setting it up following the instructions from YouTube. I couldn't work out how to set up the WiFi to get access to the cloud I wanted as the next day I went away.

It told me (from memory) that KH was about 9 vs 8.3 for Salifert. I thought this was strange as I heard Salifert is inaccurately high reading so I expected the KHD to read say 7.7 or lower.

I also can't see the results in charts and have no history prior to the 15th.

Now when I returned (13th) it was still reading high - but even higher vs Salifert - and my Alk was much lower - 7. I just tried to dose conservatively - I set up the LAN and then tried about 6 attempts on the Wifi before seemingly miraculously it connected.

(In this period I lost some acros that I thought I may - like 2 deepwater / smoothskins) but my Torches (which I think don't like low Alk) looked fine. I also tried 3 different Salifert KH test kits and once I tested from 2 different one after the other - they read within 0.1 of each other. I have a science degree and that included chemistry and marine science. So I am really particular about consistent testing.

So I didn't recalibrate it and it was off - but I ran a test at 00:26 (15th) and it read 4.2

The next morning my Alk was at 6 on Salifert. I reset up the KHD, recalibrated it - following the YouTube again. KHD was reading 4.9 at 10:26. My torches are still fine. Whilst my Salifert tests stayed between 6 and 6.4 during these few days and my KHD read 5.0 at 22:26.

Ok so it's a few days later - Salifert tested 7.1 - I moved it up slowly.... KHD is showing 5.7. (last night it was 5.9 when Salifert was 6.8)

So my question is what should I do now? Like I feel like my clams and my torches would look terrible IF my KH really is under 6. My indicator corals (Duncan and a Goniopora) look normal - the Goni didn't like the higher Alk so it looks better than before I went away.

Like do you think the KHD results could be accurate now since recalibration? Is there a smart way to recalibrate from here?

Generally I am just not confident in it - The setup was massively frustrating and that it doesn't connect to your phone immediately is not good enough. Still I can get past that - I just want a quality automatic alk tester that lasts (I expect this should) and is accurate. So I really want to find a way to be confident in the results.

Thank you ;)
Sunny

Worked out the charts - so no worries there ;)

Hello Sunny,

The best way to confirm the KHD accuracy is to use the 7.5dkH Reference solution. Any other form such as comparing it to a traditional test kit is not exactly an apples-to-apples comparison.

During setup it is also especially important that you measure your sample tubes as precisely as possible. If need be, you can calibrate the pump heads using a digital scale.

If the KH results from your KHD are not consistent with each other, check your tubing for any air bubbles.

Thank you - that helps ;)
Mine didn't come with a reference solution and it should. Really please include that - like 50ml - then we can test our other test kit against it and we will be more confident.
Best,
Sunny

I went to get a reference solution from my LFs. They don't have one.
I get the KH to run 2x per day - Since I reset it all up it has read 6.0, 5.9, 5.7, 6.1, 6.3, 6.0, 6.0, 5.9, 5.8, 6.0
You would think it is now reading consistently (even if it's consistently off) that would be fine.
However, according to the 3 different Salifert test kits I have used in that time my kH has jumped from 6.9 to 8.5 (yes I tested it last night to check and thought it was strange) and tested before the test (2 times) and then after the test and I got 8.3 to 8.5 each time. Plus I flushed it - made sure there were no bubbles during the test - I measured the lines as instructed when I set it up.
But anyhow if I am testing with multiple test kits - even if they are out - they are consistent when I test at the same time. Then my KH rises by a significant amount according to my all test kits but my KHD says there is no change.
If I did something wrong I would expect the KHD results to fluctuate - like if there were bubbles - or if I measured the length inaccurately then the results would be consistently inaccurate. I will get the store to check it.

I think we may be good - reset it up again and re-calculated and calibrated everything - very close to Salifert now after 3 tests so that's a big positive