My Hanna test are off from LFS tester

[Nikoliter]

I took my water into the LFS today to double check water parameters. I use all Hanna testers except for magnesium which I use salifert. I was surprised at a few differences and I don’t know what to make of it.

My at home test:
Alk 150
Calcium: 440
Mag: 1400

LFS test:
Alk: 130
Cal: 330
Mag: 1,100

These are some big differences. My lfs uses the api aquaspin test. I checked my Hanna reagent and it is not close to expired. I tested again and keep getting close to the same readings. The mag level was very surprising since I use tropic pro marine which comes with 1350ppm, and I dose mag to get around 1400, and didn’t think tanks consume a tremendous amount of mag to begin with.

What are your thoughts? Are my readings from
Hanna off or is the lfs aquaspin giving bad readings ?

 

[Mxracer65]

Personally I would try a 3rd source to be certain what is going on. I feel it could be easy to get false readings from about any test kit.

 

[Duffer]

Personally api sucks no matter who uses it…I would trust your Hanna..also what more important is keeping them stable so I would just keep on testing with your parameters…I use Hanna and did icp tests and they are fairly close

 

[brandon429]

Aquaspin can’t read ammonia correctly why believe it as the right one / search out aquaspin measurement threads to see

theres only two on the site, with both ammonia readings wrong, so that’s a bad start. Costly machine, and inaccurate 2/2 so far for ammonia.

 

[brandon429]

I struggle to find any test kit comparison thread on this site where varying brands line up. Does any of us know what the accurate measure is, at any time, for any param or do we just sell ourselves very well when believing

 

[X-37B]

Hanna for alk
Salifert and Elos to double check
Salifert for Ca, Mag, K, are pretty accurate.
Hanna always reads .3-.4 higher than Salifert and Elos going on 2.5 years now for alk.
Salifert and Elos are alwaya the same.

Just got back my Triton ICP.
They dont test alk.
Mine Triton
Ca. 410. 436.
Mag 1350. 1364.

Using Hanna for po4.
Po4 .031. .037

Salifert for K
K. 410. 436

I trust Salifert for all including alk.

The most important thing is that your reading is close every time whatever you are using. This leads to overall stability.

 

[jfoahs04]

Stupid question, but did you make sure to clean off the vial (finger prints, water droplets) before doing the Hanna test? I’ve had surprising, almost always low, results when I haven’t been careful about wiping off the vial before testing.

 

[X-37B]

The OP had higher results than the lfs. Mine is always clean and always reads higher too.

 

[saltysam]

As someone that uses an API aquaspin I have run into results that were indeed off from the red sea tests I also use. It is important the machine stays impeccably clean inside, any dust on the lenses will throw results. It also depends on how the cartridge is loaded. If done properly, the results are within tenths of other drop and titration tests. If something is off in the test see if the lfs will do a test to compare, with you there.

 

[aSaltyKlown]

What does your tank look like, do corals look good? If so, I'd say your test is the more accurate, the LFS numbers are very low. It would be best as many stated to get a 3rd test done with a different test.