Hanna Phosphorus checker unreliable ?

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Kai K

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I had issues with mine until I tried:
Cleaning the beaker with microfibre at each stage.
Inserting with the hanna 10ml facing forward each time.
it is v sensitive to micro bubbles and marks on the container.
+1
Being very precise and consequent with the above will get you steady results.
Also it's important to not have your battery running low.
 
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DE FISH

DE FISH

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Ok so new vials new pack of reagents new scales to measure 10ml

two separate tests both from scratch
I always trusted this meter until running more than one test I do not trust this checker at all

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sick and tired of this

ato is off as I’m wanting to raise salinity so that’s ruled out washed vials with deionised water. time to get in touch with Hanna
 
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DE FISH

DE FISH

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I’m not looking for exact readings each time but would expect to get at least the accuracy rating stated for the checker.
 

gbroadbridge

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I use 0.01g scales from Amazon, cheap to buy, seems a bit extreme but after reading someone had an issue with the line being in the wrong place, I tried a syringe but that too wasn't very accurate either as the margins we are talking here are so small, I already had the scale for making a salinity solution so ended up using the scale, works great, trying to get the exact amount in the vial each time by eye isn't easy.

Yes 10ml is 10g.

I had read a few times of people storing their vials with rodi water, but to me that seemed pointless unless you also took care of the glass on the outside too so yes I also store the vial in a little tub of rodi water, the lid is ceramic or similar so is fine in the water.
10ml of seawater is 10.26 grams
 
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Randy Holmes-Farley

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I’m thinking I’m going to have to buy the reference fluid although I’ve got a new pack of Reagents and new vials I’ll run two or three tests tomorrow See if I get any consistent results then I’ve covered every variable i possibly can. If all fails reference fluid and hopefully a new checker from Hanna if it is indeed an defective checker considering the amount I’ve spent with them.

FWIW, Hanna "reference" fluids are not very useful, IMO. They only check electronics, not whether reagents or procedures will lead to correct results. Far from being a true way to test the method being used.
 

Randy Holmes-Farley

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Good point 10g would be H2O only. There is more just salt in there so scale option is out of the window

Why is a scale option out the window? If you have a good scale, mass measurement is often more accurate than volume measurement, and we know the density of seawater at any given salinity.

That said, aquarium water volume measurements are not causing more than a tiny change in phosphate readings.
 

nereefpat

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I guess I wouldn't be that frustrated. The value is between 0.11-0.18 ppm phosphate. That's probably about as close as you're going to get with a hobbyist level kit.

Are you going to change your tank management depending on which of those values is 'right?'

FWIW, I would measure volume with a syringe, not a scale. If you wanted to be really accurate, a pipette is best.
 
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I had the same issue with Hanna Alk checker. It would read +- 1 dkh depending on the vial I use. I ended up sticking to a single vial and the issue seems to have been resolved.

Have you compared your results to another test kit?

I've heard the Hanna tends to read high on alk, though it could be the vial at fault as in your case?

Looking to buy one.
 

attiland

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Why is a scale option out the window? If you have a good scale, mass measurement is often more accurate than volume measurement, and we know the density of seawater at any given salinity.

That said, aquarium water volume measurements are not causing more than a tiny change in phosphate readings.
Ok it’s is overstatement but if you don’t know what is in the water (since you want to measure it) than you don’t know it’s weight either. I guess it also doesn’t matter because our test kit is not accurate.
my thinking is since there are no accurate weight than we have to get back to volume and if we really want to we can use a standard fluid to set it and than use that volume as a standard. But this is what Hanna has done for us already so why not just use that.
To be fair it doesn’t matter if the reading is incorrect and let’s say it is 1 instead of 1.01.
all we need to know that it is less ore more in tendencies so we can get a picture of what is going on.
 

Randy Holmes-Farley

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Ok it’s is overstatement but if you don’t know what is in the water (since you want to measure it) than you don’t know it’s weight either. I guess it also doesn’t matter because our test kit is not accurate.
my thinking is since there are no accurate weight than we have to get back to volume and if we really want to we can use a standard fluid to set it and than use that volume as a standard. But this is what Hanna has done for us already so why not just use that.
To be fair it doesn’t matter if the reading is incorrect and let’s say it is 1 instead of 1.01.
all we need to know that it is less ore more in tendencies so we can get a picture of what is going on.

If you know the salinity (or specific gravity), then we know the volume exactly (by mass). There's no uncertainty there (except by how well you measure mass and salinity). :)
 
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attiland

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If you know the salinity (or specific gravity), then we know the volume exactly (by mass). There's no uncertainty there (except by how well you measure mass and salinity). :)
That is exactly my point. You only know it by guessing the content. In theory (because I am too lazy to do all the maths) the same volume of aquarium water mixed from different salts weights different as the amount of dry material is different in the water.
All I am saying is I don’t think scale give you any advantage over measuring volume.
 
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