Hanna Phosphate test reading.. whats your policy?

[dwing27]

I use the Hanna handheld colorimeter to test for phosphates. Typically I will get different readings for the same test if I repeat the test. Example.. first test .05; second test .09, etc. Anyone else have the same experience? Which result do you usually trust? I know looking at the tank and its inhabitants is probably the most accurate but it would be nice to be able to pinpoint a potential issue just in case.

 

[StikHedRon]

I use the low range phosphorus tester HI736 and I have the same issues. Usually my first test is higher and the second and third are lower and usually match. Just because there is so much error in these testers I will usually test twice and find the number between the 2 results and use that as my result.

 

[Velodog2]

I have the low level phosphorous tester and see the same thing. The first reading will be high, the second much lower, then the third will be close to the second. I understand the need to follow directions but it is insane to expect to get accurate results if you are trying to catch a reaction on a particular point on its curve before it completes and stabilizes. That would be monumentally bad design. So I typically go with the second and third readings because they are more stable, and forget what Hanna says. Who knows if it's correct. Hanna is of no help.

 

[ultimatemj]

I think the published error range is +/- .05.

I also take multiple readings by using the second vial with just tank water as the C1 zeroing on second and third measurements.

 

[jordsyke]

I think that if you are getting numbers that low that you are where you want to be. These arent science grade testers and can only give you a ballpark figure.

 

[ultimatemj]

Interesting point, there do seem to be a lot of folks very stressed out when their P04 is any higher than .01, but to this point I haven't seen much difference in coral behavior below ~1.0.

Based on all the comments in the forums I was panicking at 1.85 and worked to get down to .1x and haven't really seen any difference.

Granted I have minimal SPS and mostly LPS, zoas, & softies.

For reference, here's my Space Invaders at 1.35 P04

I'm now at .08 and I actually see 'less vigorous' feeding.

 

[rayn]

1.35! I was freaking when I seen mine at .48. How did you go about lowering it?

I usually rely on the second test as well.

 

[ultimatemj]

Gfo

 

[richiero]

Sounds like they are a waste of money and not so cost effective. I will stick to my salfert text kit. You do only get 25 test before having to buy refills correct?

 

[ultimatemj]

Why is +/- .05 a waste?

I was just saying don't freak if you numbers are t where you want them

Is the salifert more accurate?

 

[richiero]

3 test a week or maybe more and you are paying for refills all the time

 

[richiero]

You get 60 test with salifert

 

[richiero]

Even more on the alk and cal as apposed to the hanner.

 

[ultimatemj]

Maybe when measuring to see impact of something your doing.

Now my P04 is below .1 only I'm testing once a week or so to make sure it doesn't bounce.

I suspect it will become a monthly test

 

[ultimatemj]

I hate my Red Sea cal test...I'm colored blind and can't tell when it changes color! Lol

 

[P3FE]

I own the same Hanna PO4 test and test once a week. Back in december Mr. Saltwatertank did an interview with Dr.Tim and discuss accurate testing, specially PO4. In the interview Dr.Tim pointed out that PO4 testing vials actually retain PO4 unless you can actually have a new tube every time or give the ones you have an acid bath. Anyways I can go on with their disscusion but its easier to go to his website, search the interview and listen to it, very good information if you ask me. At the end of the day, if theres no algae problem, and the corals are thriving, theres no need to worry about specific numbers, just keep doing what you are doing and enjoy your tank, thats my take.

 

[Velodog2]

Sounds like they are a waste of money and not so cost effective. I will stick to my salfert text kit. You do only get 25 test before having to buy refills correct?

Actually I think you get 5 reagent packs. First thing I did when I opened the box was go online and order more. And frankly now I don't even really use the kit often at all anymore because of the uncertainty of the readings.