Hanna Meter Readings

[MoReefer]

I recently purchased a Hanna LR Phosphate meter to help track my progress of lowering nutrients after a algae bloom. I have been consistently getting readings of .06 with no change after 2 weeks of running GFO in a TLF reactor 2/3 full. There has been no reduction in PO4 according to the meter.

My process of using the meter has been this:
Fill the cuvet with 10ml of tank water from a 5ml syringe
Cap and wipe the cuvet with a clean paper towel
Place the cuvet in the meter and lock in place
Zero the sample
Remove the cuvet and add the reagent.
I add the reagent by cutting along the dashed line with scissors
Pressing in on the sides to spread the envelope open
Grip the opening and tear the sides open, kinda like opening a microwave popcorn bag.
I found this makes it easier to get the entire reagent contents out of the envelope and into the cuvet
Recap the cuvet and swirl in a circular motion for 60 seconds. Ive found almost all of the reagent is dissolved.
Clean the reagent with a clean paper towel and place the cuvet in the meter locking it in place.
I press “Read Timed” wait for it to read “SIP” and press “Read Direct”
I rinse the cuvet with fresh RO/DI water and store upside down on a clean papertowel.

On my last test I cleaned the outside of the cuvet with an alcohol wipe before Zeroing and Readings. Still I consistently get .06. I have been running GFO on the tank but I have not seen any decline in PO4 from the Hanna readings. Does anyone think I may be using the meter incorrectly and getting inaccurate results?

Does anyone live near Springfield MO and have a meter to compare to?

Thanks

[lukinrats]

I posted the following reply to a thread similar to this, a few days ago... I am putting it here for you, because it is likely just as relevant in your situation

<a href=showthread.php?s=&postid=13245316#post13245316 target=_blank>Originally posted</a> by lukinrats
This may be a little misleading:confused: ... You may want to check your RoDi water... You see the meter has a strangely broad margin for error, or accuracy... I was testing my water, and getting the same results... I started reading the literature on the meter, and noticed that hanna states the meter has an accuracy of +/- .04 ppm... So this meant that if my meter gave me .08 ppm, that it could actually be .04 ppm, or it could be .12 ppm... So in order for me to know what my readings meant... I decided to check my RoDi... I had just changed all my filters, and the water was reading 0 TDS... I did a PO4 reading on the RoDi, and I got .04 one time, and the next time I got .05... Then, just to verify this, I read the RoDi water with both of my liquid reagent kits... Both showed no change in color.

The conclusion that I came to, and that I am comfortable with, was that my meter is going to read .03-.04 ppm high... I can even check the water coming from my reactor, filled with new GFo, and it still will read .03-.04 ppm... So it really does not matter how many filters, Di resin, Gfo I run my water through, the hanna is still going to read a little high... So, anytime that I check water with my meter, I always start by subtracting .03 ppm from the result... I feel comfortable with this.

I suspect that each meter is different, and that you should do whatever you need to do, to make sure you generate a PO4 free sample of water, then check it with the meter... Take whatever reading you get from that sample, and subtract it from all tests you make with that batch of reagents... Whenever you get new reagents or cuvets, then you will need to repeat this step in order to verify... It may end up that your meter is not off at all, and that the PO4 free sample yields a 0 ppm reading, but a buck gets 10 it will read a little

Still the best way in the hobby to check your water for phosphates IMO... it is probably the most important thing you will have to measure in your reef, to keep everything healthy, and looking nice.


Later,
NathanS

[Yinger]

did you check the effluent? you could have exhausted your GFO if your po4 was high to begin with.

[Paulairduck]

<a href=showthread.php?s=&postid=13266273#post13266273 target=_blank>Originally posted</a> by lukinrats
I posted the following reply to a thread similar to this, a few days ago... I am putting it here for you, because it is likely just as relevant in your situation


That is something good to know, Thanks!!

[MoReefer]

Lukinrats, Just wanted to say thanks. They makes perfect sense.