Do You Trust The Hanna Phosphate/Phosphorus Checkers?

[chipmunkofdoom2]

I recently started testing for phosphate using the Hanna Phosphorus ULR checker (HI736). I testing phosphate a long time ago because I lost confidence that the readings were accurate, as they were always zero. I'm having similar issues again now.

I tested last week and got a reading of 0.06 ppm. This was my first test in a long time, but it seemed to make sense. I tested again today and the reading was zero. I tested again to confirm, the reading was still zero. The only changes I made since last week was skimming a little wetter and doubling the amount of phosphate I dose per day from 0.01 ppm to 0.02 ppm. I've been dosing 0.01 ppm of phosphate every single day for about 3 months, and 0.02 ppm every day since last Sunday. I really struggle to believe my phosphates are 0.

For some background, my system is 80g (40g breeder with 50g Rubbermaid sump). I have three small fish, a coral beauty angel and two clowns. I feed two cubes of frozen food per day. I also dose 0.02 ppm of phosphate every single day. For nutrient export, I dose 5 ml of vinegar per day and skim. I do a 10% water change once a week. I have 12 - 14 small SPS frags. The only unhappy frags (a monti, two birds nests) have been unhappy for weeks. Everything else (acros mostly) is happy and growing. Specs:

Salinity: ~35 ppt (53.5 mS)
Alkalinity: 10.4 dKh
Calcium: 440 ppm
Magnesium: 1400
Nitrates: 25 - 50 ppm
Phosphates: 0 (apparently...)

So what gives? Do you trust the Hanna Phosphate/Phosphorus checkers? Given the information, do you think my phosphates are really 0?

 

[SMSREEF]

I bet it is correct and you are burning through all phosphate you add due to the high nitrate levels and carbon dosing.
One thing you could try is test, then add enough PO4 that you calculate to bring tank to 0.05 or 0.1. Give it 10 to 15 minutes to mix in water and retest phosphate.

 

[blstravler]

After you dose the phosphate have you tested to see if it shows up? Maybe add a little phosphate to a small batch of fresh saltwater and test it to see if the checker is working.

As far as trusting Hanna checkers goes - I do but I don’t trust the . I used to have the Phos, ALK and Cal and every time I would test with Alk or Cal I would get a different reading - usually small fluctuations but it was annoying. I only have the Phos checker now and use Salifert for everything else. I can test three times in a row with Salifert ALK test and always get the same results - not so much with the Hanna. I only use the Phos checker ever other week or so and I’m not sure I believe it 100%. I really just use the test to make sure I have some Phos but not too much.

 

[Sleeping Giant]

What are you using to calculate the ppm from ppb you're tester would show?

 

[chipmunkofdoom2]

I bet it is correct and you are burning through all phosphate you add due to the high nitrate levels and carbon dosing.
One thing you could try is test, then add enough PO4 that you calculate to bring tank to 0.05 or 0.1. Give it 10 to 15 minutes to mix in water and retest phosphate.

Do you really think it's the vinegar? This vinegar dosing guide recommends 5ml as the first week "starting point" for my tank. I've never dosed any more than that.

I suppose I can make up a solution that should have a known concentration of phosphate and test it. I guess I more wanted to get some more thoughts before moving to that step. I just hate everything about the Hanna phosphorus checker. I hate using it, I hate having to validate its readings on a standard that I have to make myself, I hate buying reagents for it, I hate that I can't just trust the readings, I hate how little time the stupid thing gives you to add the reagent and mix it, I hate it all. If there was anything better short of Hach lab equipment that costs thousands of dollars, I'd do it.

 

[chipmunkofdoom2]

What are you using to calculate the ppm from ppb you're tester would show?

The document you attached. My first reading was 20 ppb, which roughly translates into 0.061 ppm.

 

[chipmunkofdoom2]

After you dose the phosphate have you tested to see if it shows up? Maybe add a little phosphate to a small batch of fresh saltwater and test it to see if the checker is working.

No, I don't test after I dose. I usually dose phosphate at feeding time and don't really do any testing then. I suppose I could do that, or make a standard of a known concentration and test that. I was hoping to not have to do that, but that's seeming like the only option now.

 

[Sleeping Giant]

Do you really think it's the vinegar? This vinegar dosing guide recommends 5ml as the first week "starting point" for my tank. I've never dosed any more than that.

I suppose I can make up a solution that should have a known concentration of phosphate and test it. I guess I more wanted to get some more thoughts before moving to that step. I hate the Hanna phosphorus checker. I hate using it, I hate having to validate its readings on a standard that I have to make myself, I hate buying reagents for it, I hate that I can't just trust the readings, I hate how little time the stupid thing gives you to add the reagent and mix it, I hate it all. If there was anything better short of Hach lab equipment that costs thousands of dollars, I'd do it.

I use both flasks for the test, one with tank water for C1, and the other tank water and powder, I mix the powder for 1.5 minutes, then put flask 1 in tester (c1) then it says add c2, my mix is done and ready right away...then hold for my 3 minute timer.

 

[SPR1968]

You need to remember the Hanna phosphate checkers have a margin of error, the one I have is +/- 0.04 so in theory one test could read 0 and a few hours later 0.04 and so on. So check the margin of error on the instructions

If mine reads 0 I’m happy because it just means it’s very low.

 

[Potatohead]

They absolutely work, but you have to do the test procedure correctly and also use very clean vials to get consistent results.

 

[chipmunkofdoom2]

I use both flasks for the test, one with tank water for C1, and the other tank water and powder, I mix the powder for 1.5 minutes, then put flask 1 in tester (c1) then it says add c2, my mix is done and ready right away...then hold for my 3 minute timer.

This diminishes the accuracy of the test. Scratches and variations in the glass affect how light travels through the sample. The purpose of the C1 check is to allow the Checker to account for those in the final sample.

Hanna also could have just increased the test timeout from 3 minutes to something like 5. They boast that the checker lasts for something like five thousand tests. That's almost 14 years of tests if you test daily. The battery will wear out long before that. There's no good reason the timeout should have been so short.

 

[chipmunkofdoom2]

You need to remember the Hanna phosphate checkers have a margin of error, the one I have is +/- 0.04 so in theory one test could read 0 and a few hours later 0.04 and so on. So check the margin of error on the instructions

If mine reads 0 I’m happy because it just means it’s very low.

The ULR checker has an accuracy of +/- 5 ppb, which is 0.015 ppm. So my 0 ppb could be 0.015 ppm. Still, that's not much of a comfort since it was 0.061 ppm last week.

 

[chipmunkofdoom2]

They absolutely work, but you have to do the test procedure correctly and also use very clean vials to get consistent results.

I'm fastidious with my testing procedure. I work at the National Aquarium in Baltimore. The Hanna Checkers are like toys compared to some of the testing procedures we use there. I'd be very, very surprised if there's an issue with my testing procedure.

 

[Sleeping Giant]

I'm fastidious with my testing procedure. I work at the National Aquarium in Baltimore. The Hanna Checkers are like toys compared to some of the testing procedures we use there. I'd be very, very surprised if there's an issue with my testing procedure.

Why not test it there?

 

[chipmunkofdoom2]

Why not test it there?

Firstly because they're still closed, and second because they don't measure phosphates in my gallery. That's something we would send to water quality to get tested, and I can't send my personal tank samples to water quality testing. Not every week or as often as I'd like to test.

 

[Sleeping Giant]

I would say your tester is working, but I'm not sure what end result your looking for?

 

[SMSREEF]

Do you really think it's the vinegar? This vinegar dosing guide recommends 5ml as the first week "starting point" for my tank. I've never dosed any more than that.

I suppose I can make up a solution that should have a known concentration of phosphate and test it. I guess I more wanted to get some more thoughts before moving to that step. I just hate everything about the Hanna phosphorus checker. I hate using it, I hate having to validate its readings on a standard that I have to make myself, I hate buying reagents for it, I hate that I can't just trust the readings, I hate how little time the stupid thing gives you to add the reagent and mix it, I hate it all. If there was anything better short of Hach lab equipment that costs thousands of dollars, I'd do it.

Its just a guess on my part the carbon with new wet skimming.

But, I also had the same question... And like you I really hate using mine. Especially when I forget to come back and the 3 minutes are up and my result is long gone, making me do it all over again, lol

I was needing to add phosphate every day and next day it was 0. It just did not make any sense to me and I did not trust it so I tested 0, then dosed to 0.1 and tested again. The Hanna showed right where I had dosed, so I no longer think mine is incorrect. I dose PO4 based on the result.

 

[chipmunkofdoom2]

I would say your tester is working, but I'm not sure what end result your looking for?

Specifically, since I tested 0.061 ppm last week and the only thing I changed between now and then was doubling my daily phosphate dose, I would expect something other than zero.

More generally, the purpose of this thread was to see if other reefers trust their Checkers and if they had any insight into my situation.

 

[chipmunkofdoom2]

Its just a guess on my part the carbon with new wet skimming.

But, I also had the same question... And like you I really hate using mine. Especially when I forget to come back and the 3 minutes are up and my result is long gone, making me do it all over again, lol

I was needing to add phosphate every day and next day it was 0. It just did not make any sense to me and I did not trust it so I tested 0, then dosed to 0.1 and tested again. The Hanna showed right where I had dosed, so I no longer think mine is incorrect. I dose PO4 based on the result.

Thanks. I suppose the only real way to get comfortable with it is make some standards and test them to see.

 

[Stoney]

You need to remember the Hanna phosphate checkers have a margin of error, the one I have is +/- 0.04 so in theory one test could read 0 and a few hours later 0.04 and so on. So check the margin of error on the instructions

If mine reads 0 I’m happy because it just means it’s very low.

I think that number is accuracy, not precision. I can get the exact same reading 2, sometimes 3 times in a row. Average is usually 2-3 ppb difference between readings, but it's generally very precise.

@chipmunkofdoom2 maybe the vial or syringe was dirty when you measured 0.06. I used to do multiple tests in a row until I got consistent readings and the first measurement was always high. I started soaking the syringe in tank water for an hour before tests and always get consistent readings now. But yea I absolutely hated the thing for awhile too haha