Hanna Phosphorus Checker Inconsistent

[living_tribunal]

I bought some 10mm syringes at the hardware store and have found that those are much easier to use for filling the cuvette with the same amount every time. It's an extra step and I wash the syringe with DI afterward but it's easier for me than trying to see the meniscus.

As far as shaking, I shake the bottle for the first 20 seconds and then upend it repeatedly for the remainder of the 2 minutes. I will check and swirl it a bit to remove any bubbles at about 1:40 and then slide it carefully into the meter and push the button at 2 minutes.

I really like the Dkh meter because it doesn't take so long!

This is really the only reliable phosphate kit around so you just have to take it on the chin. It looks like my phosphates are around .01.

I got a reading of 0, 2, and 0. Everything was exactly per the instructions.

I was getting like 64 then 106 earlier, etc. I think this is actually what my levels are. I’d be confused if they were straight 0s.

Thanks for the help.

 

[blackflme]

I’m currently having the same issue. It’s been all over the place for me today.

Can you elaborate on 4?

I’m confused by why you would need to put the cuvette in tank water. I just rinse mine with tap after I’m done.

So I do this (should say did this) because when I contacted hanna, thats one of the tips they gave me. After rereading my comment, it doesn't seem as clear to me as it originally did. Hanna told me to quickly rinse the cuvette with tank water BEFORE you fill it with 10ml of tank water for the test. I think that is just so any residual tap water doesn't dilute the results.

When I started (and still have been getting very consistent results) I made two changes. Use a syringe, don't just fill to the 10ml line. I also started rinsing with tank water. I have noticed that using a syringe and getting the exact same amount of water in the cuvette was really the key here.

Check to see if the cuvette is properly filled. The picture below is an example of where to read the water level. I didn't know about the "concave meniscus" until Hanna told me. If you haven't either look at the cuvette when you fill with water, you will notice the meniscus

 

[Joedubyk]

I HATE my hanna phos checker. ALWAYS get random results.

 

[Thales]

I don't think these testers are the "gold standard" or the "only tester available" as mentioned earlier. I think they are inexpensive and easy to get so they get bought a lot. You can get a Hach Dr890 on ebay for around 500 bucks. You can get the new version for around a grand. I use the DR890 for phosphate and nitrate, but they can also test a lot more stuff. I know, they cost more money, but they do exist and are used for for more applications than aquaria. YMMV.

 

[living_tribunal]

So I do this (should say did this) because when I contacted hanna, thats one of the tips they gave me. After rereading my comment, it doesn't seem as clear to me as it originally did. Hanna told me to quickly rinse the cuvette with tank water BEFORE you fill it with 10ml of tank water for the test. I think that is just so any residual tap water doesn't dilute the results.

When I started (and still have been getting very consistent results) I made two changes. Use a syringe, don't just fill to the 10ml line. I also started rinsing with tank water. I have noticed that using a syringe and getting the exact same amount of water in the cuvette was really the key here.

Check to see if the cuvette is properly filled. The picture below is an example of where to read the water level. I didn't know about the "concave meniscus" until Hanna told me. If you haven't either look at the cuvette when you fill with water, you will notice the meniscus

That makes a lot more sense, I really appreciate the follow up.

I was able to start receiving accurate tests because of this thread. Thank you sir!

 

[Thales]

Were you using the baster for anything else besides water testing?
A gap between test results of .07ppm to .6ppm seems too extreme to chalk up to meniscus issues, especially if you were being consistent in how you were filling the cuvette. Thanks!

 

[living_tribunal]

Were you using the baster for anything else besides water testing?
A gap between test results of .07ppm to .6ppm seems too extreme to chalk up to meniscus issues, especially if you were being consistent in how you were filling the cuvette. Thanks!

The meniscus issue was the cause for huge jumps like this for me. When I didn’t have it set properly I was receiving readings from 64-104.

After I set the exact meniscus on the line, readings were 2.

 

[Thales]

The meniscus issue was the cause for huge jumps like this for me. When I didn’t have it set properly I was receiving readings from 64-104.

After I set the exact meniscus on the line, readings were 2.

How did you set it previously? I don't see how the small amount of water contained in the meniscus can result is such major changes. Minor changes for sure, but 50%? Thanks!

 

[living_tribunal]

What do you mean set it?

Side note: I still think something is off. I dosed .01 phosphate to my display last night and the test kit is still coming back as zero.

I tested my frag tank which currently has really small cyano spots throughout and it tested 0 as well.

Not sure what the h*** I need to do! Was hoping I’d finally be able to get an accurate phosphate reading :/

 

[Thales]

I mean how did you decide where full was - the top of the meniscus or the bottom or somewhere else? Sorry for the confusion - you said "When I didn’t have it set properly..." so I used the same terminology.

 

[living_tribunal]

I mean how did you decide where full was - the top of the meniscus or the bottom or somewhere else? Sorry for the confusion - you said "When I didn’t have it set properly..." so I used the same terminology.

Haha no problem, specifics are kind of becoming important with this kit.

I filled until the outskirts of the water level touched the line. This caused very high readings which I tested 3 times (completely new water fill and regent) with similar yet more extreme results.

I just dosed another .01 phosphate to my display and re-testing. I hope it’s able to pick up on it. Otherwise, I’ll have to contact hanna.

 

[living_tribunal]

It picked up on it and gave me a 6 reading which is very nice to see. I had been taking the water from a spot in front of my pump. I’m wondering if that could have caused some issues?

This reading seems very accurate considering the dose last night. I think I’m getting closer.

 

[Thales]

What does 'gave me a 6 reading' mean?

 

[living_tribunal]

What does 'gave me a 6 reading' mean?

The meter gave my water a 6ppb phosphorous, or .018 phosphate, result after testing.