PO4 Phosphate Test Kit Shoot out: NYOS Elos Pro Salifert Hanna Checkers Seachem

[jason2459]

Here we go again. Testing out several different brands of Phosphate test kits. This is a continuation of several other testing sprees I've been doing recently. Currently my go to kit for phosphates is my Hanna ULR Phosphorus checker. Going into this shoot out I didn't foresee that changing. BUT I was also not expecting to get swayed away from using API for nitrates. After the nitrate kit shoot out I am looking at going with Salifert for it's very quick and easy testing procedures and ability to easily see that the results are below 5. So, keeping an open mind here.

The Nitrate Kit shoot out:
http://www.reefcentral.com/forums/showthread.php?t=2538789

Comparisons between Salifert and API calcium and alk kits done a while back
http://www.reefcentral.com/forums/showthread.php?t=1927189

Testing my own testing abilities vs. Triton
http://reefcentral.com/forums/showthread.php?t=2537234


For this phosphate kit round I've got Nyos, Salifert, Elos Pro, Seachem, Hanna 713 Low Range ppm Phosphate Checker, and Hanna 736 ULR ppb Phosphorus Checker.

I've found my phosphates in my system swing a lot between .02 to .09 at any one time most likely coordinating with my very heavy feeding routine. Pellets automatically dropped in 4x per day, at least 2-3 feedings of something meaty per day, and at least one sheet of algae per day. My target that I find works for me and everything is happy is between .04 and .08. My Duncan and Fiji Yellow Leather hates it when phosphates get to low, to high, or drops. They are a good indicator of any one of those events.

So, to make sure I get a sampling of the same water to be tested by all the kits and don't get caught in a swing in the middle of testing between the kits I called upon my minions to assist. I rinsed out the cup with my tank water several times and just scooped it out using this for all kits.

I plan on doing one more all out brawl between most all my kits and probes vs. Triton and Aquamedic AWT in a few days which will be a new thread.


And now for my typical blurb that can be skipped and go on to the next post for the testing results, comparisons, and review.

I've always been a fan of API when I can use them as they are cheap, consistent for me, and accurate enough for me. I don't try or want to try to run a ULNS system. I aim to be in a range for pretty much all parameters based on what Randy Holms-Farley lists over in this great article
http://www.reefkeeping.com/issues/2004-05/rhf/index.php

I find the key to getting consistent results is making sure I do all the tests ( from prep, execution, reading, and clean up) is done as exactly the same as possible every time along with making sure the reagents are not close to expiring.

 

[jason2459]

Hanna 736 ULR ppb Phosphorus Checker

Hanna 736 ULR ppb Phosphorus Checker

First up is my current favorite and go to. The Hanna 736 ULR ppb Phosphorus Checker. I feel I get consistent results and accurate enough for tracking my phosphates and to know I'm in my target range. But I'm not going to be so close minded that there can't be or hasn't been issues with this checker for other people.

BeanAnimal did an excellent review on it as well. He wasn't so impressed and experienced issues with bad reagents. Which can be an issue with any test kit of any brand for any kind of test.
http://www.beananimal.com/other/hanna-hi-736-checker-hc-opinion.aspx

Cost wise its upfront cost is more then some others at around $40-$50 but the long term cost is reduced by being able to just buy the reagents for like $8 for 25 packets.

This technically is a phosphorus checker so to get the phosphate numbers we commonly look for and recommended to be at around .03ppm or below there's some math to be done. There's a chart in that link above already breaking it down or just remember to

Number in ppb x 3.066 and then divide that by 1000 and you will get close enough to what you are looking for with phosphates in ppm.

For accuracy it's pretty good with a range of 0-200ppb, resolution of 1ppb, and an accuracy of ±5 ppb ±5%. Which is really pretty good if it matches what's advertised.

Which Hanna sells what they call a calibration set but you can't really calibrate the Checker. You can however use it to check the accuracy. But there is a flaw with this one in that it uses two vials. Which if there are in flaws and differences between the two vials either initially or over time with use it will cause interference making the readings inaccurate.

I did this "calibration" set for the ULR phosphorus checker and have used it a few times to check accuracy of my particular ULR Checker. So, far I've gotten readings of 98 a few times and 100 a few times. Which is about as good as I could expect to get. The reading is supposed to show 100ppb ±10 ppb or anywhere between 90 and 110. Tonight the reading was spot on 100.

Now for testing my tanks water. I have a pretty good routine down with this checker and do the same with the 713 checker as well.

1. rinse out the vials with tank water several times
2. Fill with 10ml of tank water
3. Get a packet out and flick it a few times to loosen up the powder and move away from the area I'm going to cut in a curved pattern as indicated on the packet (was doing this before they put that indicator on there as well)
4. Set the vial down with tank water and wait for 4-5 minutes doing other stuff
5. Turn the checker on and wait for it to as for C1
6. Place the vial in with the 10ml mark facing me
7. Cut open the reagent packet and pinch it open so the bottom part is creased to help funnel the powder out into the vial
8. Press the button to read C1
9. As soon as it asks for C2 I pull the vial out (never touching with my fingers at any stage of this using a lint free cloth) and add the reagent
10. Close the vial up and look at the time and gently start mixing the reagent into the water. Taking care not to form bubbles on the insides of the glass.
11. As soon as the time changes on the minute I press and hold the button to get the 3 minute timer.
12. Continue to gently mix the reagent for 1 more minute.
13. Place the vial back into the checker and wait for the 2 minutes to count down.

I find that the reagent for the ULR 736 checker dissolves a lot better then the 713 Low Range checker. Also the end result value is displayed a lot longer on my 736 ULR checker.

And the results tonight are on target with the range I am usually in.

11ppb phosphorous converts to 0.03ppm phosphates.

 

[jason2459]

Hanna 713 Low Range ppm Phosphate Checker

Hanna 713 Low Range ppm Phosphate Checker

The Hanna 713 Low Range ppm Phosphate Checker is the first Hanna Checker I got and it's always been OK. It's not any cheaper then the ULR and not any more accurate but the resolution is lower. I would recommend if anyone is getting a Hanna Checker to go with the 736 ULR.

Testing procedures are exactly the same but I find the reagent to not dissolve as well. The reagents are not interchangeable. There is also a "calibration" set to go with the 713 checker as well. Except it is open for a lot more error. With the 736 Reference set the 2nd vial is already set. With the 713 Low range reference set the 2nd vial requires you to take out the stopper (not easy) and add some reagent and mix it up. This creates a much greater room for error and interference to enter into the picture.

But after comparing against the reference set my checker is with in range which is supposed to be 1.0 ppm ±.08 ppm (.92 - 1.08ppm range)

http://images.tapatalk-cdn.com/15/11/19/56bea504274aae16a1d0ebd43ad6d55a.jpg[img]

For my results with my tank water is where the accuracy range comes in which is ± 0.04 and with my tank being somewhere around .03ppm means I can easily read 0 and between anywhere up to at least 0.04ppm.

[img]http://images.tapatalk-cdn.com/15/11/19/d5e56a5bd641642a38057f6c1ace2acf.jpg


I really see no reason to get this checker as the ULR checker is slightly better but the same cost. IMO

 

[jason2459]

Seachem Laboratories Multitest: Phosphate Test Kit

Seachem Laboratories Multitest: Phosphate Test Kit

I really had no expectations at all with the Seachem Phosphates test kit. I saw it, it was cheap ~$13-15, and said why not. For the price it competes against API but the advertised resolution and accuracy is much much better that API can't come close to touching.

"¢Range: 0.0 - 3.0 mg/L (ppm)
"¢Precision: 0.001 - 0.1 mg/L (ppm)


I was also pleasantly surprised it even came with a reference solution to check accuracy. What I didn't like was a dropper to hopefully get an accurate amount of water. Though it's a small amount I would have rather of had a syringe.

Execution was extremely simple and quick. A small amount of water is pulled with the drop and place in a little curved disk plate. Then a few drops of a solution and a spoon full of reagent and a quick mixing with a little stir stick. Wait 5 seconds and look.

Resolution really then depends on your ability to accurately differentiate between shades of a color gradient which can be impossible for some. I found it difficult myself.


I also found the reference solution to be slightly off but really at the price of this kit not that bad. For someone just wanting to make sure they are under .1 and wants a cheap kit I find this a perfect solution.

I took the sleeve off that's supposed to help you see the gradient better to compare against your solution to get a better picture.

I think I see around .05ppm for my tank water?

The reference solution is supposed to be 1.0 but I matched it more to 1.5

For a cheap easy solution for anyone new, just trying to get phosphates under .1 and doesn't want to waste a more expensive kit's reagent until it gets there, or just to use as a quick/cheap check against what you have I like this kit.

 

[jason2459]

Salifert PO4 Profi Test

Salifert PO4 Profi Test

I had high hopes for this one. The nitrate test kit was super easy and super quick to use. If trying to stay under 5ppm Nitrates it was perfect. The PO4 kit is more expensive then the Seachem but cheaper then the Hanna Checkers upfront but once the reagents are out you buy a whole new test kit. Which is around $20-28.

Like with the Nitrate kit there's a way to get two sets of resolution with this kit. With the Nitrate kit it's a quick flip of the card and look from the side then divide by 10 to get your results. With this kit it's different. You double the amount of sample water and reagents used. Then divide the results by 2 so .03 becomes 0.015.

Sounds good right? Well it again depends on seeing the difference in shades of pale blue to less pale blue... At the high resolution just like with the Nitrates kit I found it the hardest to read the results of all the kits I've tried out.

So, with the standard procedure I see about 0 phosphates.

Then doubling the amount of water and regents I see about 0 maybe a shade close to the .03(.015)...

My hopes were dashed for this one. I don't see any use for this one. If one just wants to easily read if they have over or under .1 there's the seachem at a cheaper price.

 

[jason2459]

looks like the img tag above for the 713 check was done wrong.


This is the result from using the "Calibration" Set which is in range with the expected 1.0

 

[jason2459]

Nyos High sensitivity seawater phosphate test kit

Nyos High sensitivity seawater phosphate test kit

I wasn't planning on trying this kit out at all. I was kind of disappointed in the Nyos Nitrate kit but decided to give this one a go anyway. Cost is equivalent to Salifert in the $20-25 range.

The range is there

Measurement Range:
0.025"“1.0 mg/l PO4

but was skeptical on the ability to read it. Especially after seeing the color chart and instantly thought this was another waste as there's no way I'm going to be able to tell the difference between different shades of white. I thought the blue of the salifert was bad. This was worse just looking at it for the first time.

Then I went on the perform the test and I find out I have to wait 10 minutes after adding the solution and reagent? I thought was a joke and waste of time.

But then after 10 minutes were up and I lined up the vials along the color chart I was actually able to tell the difference between shades of white. What I read was 0.05ppm Which actually matches up with what I think I read with the Seachem kit.

This certainly seemed very disappointed on just opening it up and executing the test but after all said and done it wasn't that bad at all and more impressed with this one over the Nitrate kit. I would certainly recommend this kit over the Salifert. It was much easier to read then the Seachem at the lower numbers.

 

[jason2459]

Elos Professional Aqua Test Kit Phosphate

Elos Professional Aqua Test Kit Phosphate

I was most looking forward to trying this kit out. It's the most expensive out of this group at around $45-$50 but has gotten several really good reviews. But I was let down by the Nyos Nitrate in my last shoot out.

The Elos professional phosphate kit has a higher resolution then the none professional version and more expensive to go along with it. The range is certainly there for our needs as advertised:
"¢Precisely Measure LOW LEVEL Phosphates (between 0.008 and 0.14 ppm)


The kit was setup much like the Nyos kit with an A and B reference vial to drag along a color chart. But the Elos included a much greater range of values on it's color chart (minus seachem being funny with a bunch of individual tick marks.) The colors went from shades of yellowish off white to blues.

The execution was pretty easy and straight forward. It did have an extensive 3 minute mixing. But after that was done I found it the easiest of the color chart tests to read. It also came very close to what the Hanne ULR checker came up with.

I got a reading of about 0.024

Minus the cost I was very happy with this kit. It was easy to use. Fairy quick with a 3 minute mixing period. Easy to read but I still see many having issues with this or any of the color matching based test kits. It was a one time use but it matched up to what I've considered a very reliable test with the Hanna ULR Checker so it seems to match up with other's reviews about accuracy.

The cost certainly is a factor though but it's not as much as what I would consider the best PO4 kit we have with-in a hobbyist's budgets reach and that's the Hach PO-19 test kit which is around $100. This Elos kit seems like a fairly good alternative for those wanting a higher resolution kit that's half the cost of the Hach.

 

[jason2459]

Overall I'm happy with them all except for the Salifert due to the difficulty of trying to read it's results. I think I hit the perfect time as my tank was right at around the recommended phosphate levels of around 0.03 or less. I was able to really see what test kits could read those levels not really accurately but more so just the ability for me or anyone to be able to read the results properly.

Winner for me is still the Hanna 736 ULR for over all cost and performance. The Elos Pro is my second choice in all this for high resolution checking. For basic quick cheap checking the SeaChem hands down.


Hanna 713 Low Range
Pros:
- Long term costs brought down through reagent purchases
- Easy to read digital output
- has a reference solution available

Cons:
- Initial upfront cost is higher
- Reagents seem to have QA issues at times
- Reagents to dissolve as well as it's alternative 736 ULR Checker
- Can be complex to perform the test to get consistent results
- reference solution involves user to mix in reagent creating room for error
- vials require care to not mark up that could cause interference with the optical reader
- Results show time is quick


Hanna 736 ULR Phosphorous
Pros:
- Long term costs brought down through reagent purchases
- Easy to read digital output. Best for people that have a hard time with color charts
- Resolution and Precision in the range we really need it
- Reference solution available and no user involvement needed to use
- Results remain displayed longer then the 713

Cons:
- Higher initial cost
- Reagents seems to have QA issues in the past (I haven't experienced that with this checker)
- Can be complex to execute the test
- Vials require care not to mark up as well

SeaChem
Pros:
- Lowest cost
- Quickest and Easiest to perform
- Easy to see if your below .1 or above
- Comes with a reference solution

Cons:
-Under .1 and it's extremely hard to know where in the gradient chart you're at
- reference solution isn't dead on but good to see how to color match

Salifert PO4
Pros:
- quick and easy to perform

Cons:
- Hardest to read the results at the high resolution even when doubling everything
- Not worth the cost as there's plenty of easier to read solutions out there for the same price

Nyos
Pros:
- Ended up being easier to read then I thought it would be
- Decent resolution and color matching in the range we are looking for
- easy to perform

Cons:
- Took the longest to perform (not a huge deal but something to note)
- Easily could be hard for people that have a hard time matching colors as there really weren't colors to match but shades of white

Elos Pro
Pros:
- Easy and fairly quick to perform
- Highest resolution of the color matching kits with more color samples to match against
- Seems fairly accurate and found it the easiest to read of the color matching kits

Cons:
- Most expensive of the kits tested minus the upfront cost of the Checkers
- Could be hard to read for those that have difficulty in matching colors as the shades of colors are very close.

 

[Buzz1329]

Great post, thanks.

It warmed the cockles of my heart to read Bean Animal's review, and I greatly appreciate your sharing it because based on my experience with Hanna 713, it is spot on. I am especially interested in your Hanna 736 testing method, as I just got kit and am trying to compare it with Hach test, which so far is my "go to" PO4 kit:

"7. Cut open the reagent packet and pinch it open so the bottom part is creased to help funnel the powder out into the vial
8. Press the button to read C1
9. As soon as it asks for C2 I pull the vial out (never touching with my fingers at any stage of this using a lint free cloth) and add the reagent
10. Close the vial up and look at the time and gently start mixing the reagent into the water. Taking care not to form bubbles on the insides of the glass.
11. As soon as the time changes on the minute I press and hold the button to get the 3 minute timer.
12. Continue to gently mix the reagent for 1 more minute.
13. Place the vial back into the checker and wait for the 2 minutes to count down."

This may sound crazy, but what do you mean by "gently . . . mixing"? Are you swirling or shaking?

So after you get to the C2 stage on the Checker, you add reagent and mix for one minute. You then press the button on the Checker to start the 3 minute countdown. At this point, the test tube with the reagent is NOT in the Checker? You then continue to mix reagent in the tube until the countdown reaches 2 minutes, at which point you place the test tube in the Checker?

Thanks again,

Mike

 

[Big E]

Nice job.............one thing that should be mentioned is that the Elos Colorimeter 2.0 will read their color sensitive kits per a smart phone app, so you can get a digital readout instead of trusting your eyes.

It can also log and graph the chemical data.

I don't believe it's come to market yet.

 

[Reef Frog]

An interesting series of reviews. Thanks for doing them.

What kind of room lighting did you have when you did test comparisons?

When I did the Red Sea PO4 tests, they were virtually worthless for distinguishing the low ranges under my kitchen lighting, which is a mix of halogens, white LED and light fixtures with yellow art glass globes.

The color differences were better in my laundry room where I use 6500K daylight T8 tubes with a clear plastic diffuser lens. But the .08ppm - 0ppm looked pretty much the same to me. At least I could now confirm that my PO4 was somewhere in the "OK to good" range.

Then I tried it outside on a clear day in early summer with the sun high in the sky. Now it seemed I could tell the difference between .08ppm & the 0-.04ppm range. But I never could be sure and other people had different opinions or couldn't tell when I showed it to them.

So the RS test succeeded in telling me my levels weren't crazy bad I suppose. But I was hoping for some more expert guidance on when to change out GFO and to see if I possibly could "strip" my water to 0ppm. For that, the RS test didn't help me.

 

[jason2459]

Great post, thanks.

It warmed the cockles of my heart to read Bean Animal's review, and I greatly appreciate your sharing it because based on my experience with Hanna 713, it is spot on. I am especially interested in your Hanna 736 testing method, as I just got kit and am trying to compare it with Hach test, which so far is my "go to" PO4 kit:

"7. Cut open the reagent packet and pinch it open so the bottom part is creased to help funnel the powder out into the vial
8. Press the button to read C1
9. As soon as it asks for C2 I pull the vial out (never touching with my fingers at any stage of this using a lint free cloth) and add the reagent
10. Close the vial up and look at the time and gently start mixing the reagent into the water. Taking care not to form bubbles on the insides of the glass.
11. As soon as the time changes on the minute I press and hold the button to get the 3 minute timer.
12. Continue to gently mix the reagent for 1 more minute.
13. Place the vial back into the checker and wait for the 2 minutes to count down."

This may sound crazy, but what do you mean by "gently . . . mixing"? Are you swirling or shaking?

So after you get to the C2 stage on the Checker, you add reagent and mix for one minute. You then press the button on the Checker to start the 3 minute countdown. At this point, the test tube with the reagent is NOT in the Checker? You then continue to mix reagent in the tube until the countdown reaches 2 minutes, at which point you place the test tube in the Checker?

Thanks again,

Mike

I really like my 736 ULR and haven't had any issues with it. But I'm not naive or a fan boy and not acknowledge that there hasn't been or can't be issues. But at the same time every hobby test kit out there has or can have the same issues with bad or expired reagents.

I do not shake. You don't want bubbles on the wall of the vial of microbubbles through out the water column. I'll invert a couple times slowly and swirl a bit and then invert a couple times. Keep doing that until its time to put in the Checker for the final count down which is to let anything solid settle or let micro bubbles if any in their to rise.

That timing thing is exactly what I do. But making sure I don't get micro bubbles in there helps. About 1 minute of swirling and investing then press the button to get the 3 minute timer while swirling and inverting for one more minute before placing in the Checker.

I also check one last time there are no bubbles on the sides and put the vials in the same way every time. 10ml facing me.

Nice job.............one thing that should be mentioned is that the Elos Colorimeter 2.0 will read their color sensitive kits per a smart phone app, so you can get a digital readout instead of trusting your eyes.

It can also log and graph the chemical data.

I don't believe it's come to market yet.

That's great they are getting into that. Sounds like what the iDip is attempting to do. iDip has been around a while but not for aquarium. They have a ways to go though before I'll buy one. They don't hit the ranges we need yet for all our tests and looks to have issues with consistency for right now. They are working on it and at least acknowledge there are issues.

An interesting series of reviews. Thanks for doing them.

What kind of room lighting did you have when you did test comparisons?

When I did the Red Sea PO4 tests, they were virtually worthless for distinguishing the low ranges under my kitchen lighting, which is a mix of halogens, white LED and light fixtures with yellow art glass globes.

The color differences were better in my laundry room where I use 6500K daylight T8 tubes with a clear plastic diffuser lens. But the .08ppm - 0ppm looked pretty much the same to me. At least I could now confirm that my PO4 was somewhere in the "OK to good" range.

Then I tried it outside on a clear day in early summer with the sun high in the sky. Now it seemed I could tell the difference between .08ppm & the 0-.04ppm range. But I never could be sure and other people had different opinions or couldn't tell when I showed it to them.

So the RS test succeeded in telling me my levels weren't crazy bad I suppose. But I was hoping for some more expert guidance on when to change out GFO and to see if I possibly could "strip" my water to 0ppm. For that, the RS test didn't help me.

I've been going under softwhite LEDs in my kitchen. No idea the Kelvin of them. Lots of people have issue especially with high resolution kits telling the difference between shades of colors. Digital kits are great for them.

 

[Buzz1329]

"I do not shake. You don't want bubbles on the wall of the vial of microbubbles through out the water column. I'll invert a couple times slowly and swirl a bit and then invert a couple times. Keep doing that until its time to put in the Checker for the final count down which is to let anything solid settle or let micro bubbles if any in their to rise.

That timing thing is exactly what I do. But making sure I don't get micro bubbles in there helps. About 1 minute of swirling and investing then press the button to get the 3 minute timer while swirling and inverting for one more minute before placing in the Checker.

I also check one last time there are no bubbles on the sides and put the vials in the same way every time. 10ml facing me."

Cool. Exactly what I needed to know.

Mike

 

[droog]

Awesome review(s) - exactly what I needed

Also thanks to BigE for pointing out the Elos colorimeter. I use the 736 ULR at the moment. It works well but is a bit of a pain to get all the reagent from the packet and mix within the time limit.

Will look at the Elos colorimeter test when that comes out. It may be a replacement for ny 536. One spoon of reagent, mix for 3min and scan with my phone? Seems easier. The only thing better would be a liquid reagent...

-droog

 

[00101]

My 736 procedure is slightly different. I only use one of the cuvettes for my 'calibration' and test to reduce interference from glass differences or soils. IIRC the time out for the checker to turn off is 3 minutes, so I do the full mixing before reinserting the cuvette and starting the countdown. I always grab by the cap or use a lens cloth while handling the cuvette during these procedures. Additionally, I store the cuvettes wet, completely full with RO/DI water between uses.

 

[jason2459]

Awesome review(s) - exactly what I needed

Also thanks to BigE for pointing out the Elos colorimeter. I use the 736 ULR at the moment. It works well but is a bit of a pain to get all the reagent from the packet and mix within the time limit.

Will look at the Elos colorimeter test when that comes out. It may be a replacement for ny 536. One spoon of reagent, mix for 3min and scan with my phone? Seems easier. The only thing better would be a liquid reagent...

-droog

Glad it helped. I'm looking forward to the integration of smart phones and devices. It's needs more development but if Elos has something to market soon that would be great.

My 736 procedure is slightly different. I only use one of the cuvettes for my 'calibration' and test to reduce interference from glass differences or soils. IIRC the time out for the checker to turn off is 3 minutes, so I do the full mixing before reinserting the cuvette and starting the countdown. I always grab by the cap or use a lens cloth while handling the cuvette during these procedures. Additionally, I store the cuvettes wet, completely full with RO/DI water between uses.

How do you use only one for the calibration? There are two vials in the calibration set. One is for the C1 zero reading and the other is for the C2 ~100 reading.

For the actual testing of tank water I do use a single vial. Some will use two but that introduces the chance for the test to not be as accurate as you noted. Maybe you are talking the calibration as the C1 stage and not using the Calibration Set that Hanna Sells?

I also never touch with my fingers and avoid even touching the middle of the vial. Only the bottom and the top screw down area with a lint free cloth. I use a cloth used to clean glasses or smart phone screens with. Lens cleaning cloth would work well too.

For timing I get 2 minutes of gentle swirling and inverting type mixing and 2 minutes of sitting in the checker. The first minute is while the checker display is asking for C2. The prior 30 seconds are for me pulling the vial out, unscrewing the cap, and carefully poring in the powder, screwing the cap back on, and making sure no powder got on the outside of the vial. Then I begin that gentle mixing for 1 minute. After that minute is up I will Press and hold the button to get the 3 minute timer and keep gently swirling and periodically inverting for one more minute. This leaves 2 minutes on the timer in which I will place it into the checker and close it up. I feel this gets more reagent dissolved with out harsh mixing and introducing more microbubbles or bubbles on the sides of the glass.

 

[00101]

How do you use only one for the calibration? There are two vials in the calibration set. One is for the C1 zero reading and the other is for the C2 ~100 reading.

For the actual testing of tank water I do use a single vial. Some will use two but that introduces the chance for the test to not be as accurate as you noted. Maybe you are talking the calibration as the C1 stage and not using the Calibration Set that Hanna Sells?

I also never touch with my fingers and avoid even touching the middle of the vial. Only the bottom and the top screw down area with a lint free cloth. I use a cloth used to clean glasses or smart phone screens with. Lens cleaning cloth would work well too.

For timing I get 2 minutes of gentle swirling and inverting type mixing and 2 minutes of sitting in the checker. The first minute is while the checker display is asking for C2. The prior 30 seconds are for me pulling the vial out, unscrewing the cap, and carefully poring in the powder, screwing the cap back on, and making sure no powder got on the outside of the vial. Then I begin that gentle mixing for 1 minute. After that minute is up I will Press and hold the button to get the 3 minute timer and keep gently swirling and periodically inverting for one more minute. This leaves 2 minutes on the timer in which I will place it into the checker and close it up. I feel this gets more reagent dissolved with out harsh mixing and introducing more microbubbles or bubbles on the sides of the glass.

Yes, I meant the 'calibration' in the C1 stage, not using a known standard. If you're using part of the three minute timer as mixing, you're not allowing the full five minute reaction period which may throw off your results. From when its done with C1, you have three minutes of inactivity before it will turn off, which means you have a minute (three minutes minus the two for mixing) to get the cuvette out, the reagent in, and it back in the checker. I find as long as I have a timer on my phone to show me how much time I have left its not a problem at all to get it all done in three minutes. After this you start the countdown on the checker.

 

[Jone]

Tag

 

[Buzz1329]

I HATED the 716 Hanna checker, but now I am a big fan of 736 ULR checker. I get consistent results and do not experience the probs I had with 716: dissolving reagent in test tube and transferring all of the reagent from sachet to test tube.

Thanks again, Jason 2459, for the very thorough review of all these tests.

Mike