Alk test kit discrepancy?

[pisanoal]

I've got a new 125 set up that has about 170 gallons overall. I moved coral and inverts over from my 40 and letting it sit fallow for 75 days while I great existing fish and a few new before going in. I've got some acros in the new tank that are doing fine so far.

I hadn't tested in a couple weeks due to life, and checked all the big parameters. Mag was 1200, Alk was 6.0, Ca was 400, no3/po4 were 0. All with salifert except ca which was Hannah. I've been slowly raising my mag and alk, and a little bit of calcium too. Been coming up about .2 per day. Yesterday, by accident I grabbed the Hannah checker for alk and ran it instead of salifert and was surprised to see a 166 ppm which comes out around 9ish dkh. I was surprised by the jump but I had just done a 10percent water change. I recheck with salifert and it was 7.0. Right about where I expected.

I still had the standard that comes with the salifert kit so I ran it and got dead on the 6.7 that it's supposed to be, so I have to assume that it is right. I thought maybe I had old reagent for the Hannah so I rinsed everything well and retested, got around the same. Grabbed the other vial, ran it again, same thing. Ran the test 4 different times getting a range of 160 to 166 ppm. I plan on changing out the battery tonight and trying again but that seems like an awful lot to be off for a colorimeter. Any one else have input?

I should note that mag levels are around 1300 now and ca is around 450

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[bertoni]

If the Salifert is matching the reference solution, I would trust it. Testing kit problems are all too common. You could try getting a local fish store to test the water, if possible, or get a third kit, but all those levels are safe enough, so I'd just ignore the issue for the moment, as long as the corals are okay.

 

[pisanoal]

Thanks for the reply. Well the corals are ok, the 6 was low so a few looked a little pale from stress, and the 9 is a bit high if I'm raising it as my nutrents are really low since there aren't fish yet. I do trust the salifert. My comment was more towards the Hannah. That is quite a bit off for a colorimeter test. I hadn't known anyone to have that kind of major accuracy issues with the Hannah all kit, which is really what I was asking. Would kind of suck to basically throw it out, but if it's that far off its almost useless.

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[bertoni]

The Hanna alkalinity kit has had some issues reported. It measures alkalinity indirectly, I think, so I have wondered about its accuracy for a while now.