Testing variations

[Merv49]

I've been using a Hanna Alkalinity checker for a while now but also used API. My problem is when using the API checker for quite a few months I was keeping my Alkalinity about 9 but ran out of reagent so I began using my Hanna. (though I already had the Hanna, it was far easier to test with the API) Now that I'm back using the Hanna, all of a sudden I'm having to reduce my two part dosing because my alkalinity is rising even though I've cut the dosing from 160 ml a day to 110.
Not sure what was going on I got another API test kit and it shows my alkalinity at 7. I ran the Hanna standard and the reading was accurate a 5dkh. Now which tester do I believe. Funny thing is that the standard fluid is blue and the test fluid makes the water green.
My corals don't seem to be affected but I'm leaning toward trusting the API results because I started my tank on the Hannah and really didn't see a lot of activity and when I began using the API for perhaps 8 months and running at 9dkh I saw good growth. Takes a long time to know one way or the other with corals so I'm wondering is anyone else has had this issue.

Thanks

 

[Brew12]

I've been using a Hanna Alkalinity checker for a while now but also used API. My problem is when using the API checker for quite a few months I was keeping my Alkalinity about 9 but ran out of reagent so I began using my Hanna. (though I already had the Hanna, it was far easier to test with the API) Now that I'm back using the Hanna, all of a sudden I'm having to reduce my two part dosing because my alkalinity is rising even though I've cut the dosing from 160 ml a day to 110.
Not sure what was going on I got another API test kit and it shows my alkalinity at 7. I ran the Hanna standard and the reading was accurate a 5dkh. Now which tester do I believe. Funny thing is that the standard fluid is blue and the test fluid makes the water green.
My corals don't seem to be affected but I'm leaning toward trusting the API results because I started my tank on the Hannah and really didn't see a lot of activity and when I began using the API for perhaps 8 months and running at 9dkh I saw good growth. Takes a long time to know one way or the other with corals so I'm wondering is anyone else has had this issue.

Thanks

Alkalinity test kits are the bane of my existence. I now have Salifert, Redsea, API and the GHL KH Director for auto measurements. What I have found is that the Hanna is the most consistent but that aging of any reagents will cause big problems with the readings from any kits. Shake all reagents well before every test and don't use any for more than a month or two. I still get results over 1dKH apart depending on what kit it is but at least each kit is consistent with itself.