False Reading From Hannah Checker or High PO4

[Davisc1293]

I asked this earlier but it was a dead thread. My Hanna checker is reading phosphates at .36 This whole time my PO4 has been reading high I've taken it as a false reading since I've read silicates can cause it to read high and I've been dosing silicates to cause a diatom bloom to compete with dinos. But Today after more reading I found somewhere it will only effect the hannah phosphate checker if silicates are higher then 10ppm. which my salifert kit barley shows 1ppm. Would you think my phosphates did skyrocket somehow or could it in fact be a false reading from the silicates?

 

[Davisc1293]

 

[DrinkinPepsi]

What's the water source? Have you tried to test that?

 

[Davisc1293]

What's the water source? Have you tried to test that?

i did test my rodi water after a 10% wc that seemed to have no effect on the tanks level. but did test 0

 

[Muffin87]

in fact be a false reading from the silicates?

The Hanna PO4 Checker is VERY finicky. Some CRAZY tips:

1. Take sample water before feeding. Wait for any invisible particles to settle on the bottom of the container, and use a syringe to take a smaller sample from the surface water of the original sample. That's your new sample.
2. Do not put your fingers inside the reagent pouch. Change its shape from the outside.
3. It's a TIMED test - PO4 will read higher if you wait too long before starting the test timer. After shaking for 2 minutes, very quickly make sure there are no fingertips on the vial, and start the test timer. This is why the original HI736 has such a short timer that had people often run out of time for the C2.
4. If you shake too vigoursly, the reaction will happen more quickly. The test being timed, PO4 will read higher. Use an AutoAqua magnetic stirrer to make sure the reagent is mixed with same strength every time.
5. If you use lanthanum chloride to remove PO4 and the resulting particulate hasn't been removed completely by the mechanical filtration, the reagent will break the bond between the lanthanum and the phosphate, causing the reading to be higher.
6. Clean the inside of the vial VERY well. As suggested by Hanna, I use their general purpose cleaning solution. Which is really just 0.034% hydrochloric acid in RO/DI. You can make it at home easily.

Just yesterday I tested PO4 in my coral quarantine tank FIVE TIMES. The results:

• 0.22 (vial wasn't clean probably)
• 0.06
• 0.18 (put fingers inside the pouch)
• 0.02
• 0.04

I'd totally get a different PO4 test if I wasn't terrible at distinguishing shades of colour.
You'll find plenty of threads saying the Hanna PO4 checker gives inconsistent readings.

 

[Davisc1293]

The Hanna PO4 Checker is VERY finicky. Some CRAZY tips:

1. Take sample water before feeding. Wait for any invisible particles to settle on the bottom of the container, and use a syringe to take a smaller sample from the surface water of the original sample. That's your new sample.
2. Do not put your fingers inside the reagent pouch. Change its shape from the outside.
3. It's a TIMED test - PO4 will read higher if you wait too long before starting the test timer. After shaking for 2 minutes, very quickly make sure there are no fingertips on the vial, and start the test timer. This is why the original HI736 has such a short timer that had people often run out of time for the C2.
4. If you shake too vigoursly, the reaction will happen more quickly. The test being timed, PO4 will read higher. Use an AutoAqua magnetic stirrer to make sure the reagent is mixed with same strength every time.
5. If you use lanthanum chloride to remove PO4 and the resulting particulate hasn't been removed completely by the mechanical filtration, the reagent will break the bond between the lanthanum and the phosphate, causing the reading to be higher.
6. Clean the inside of the vial VERY well. As suggested by Hanna, I use their general purpose cleaning solution. Which is really just 0.034% hydrochloric acid in RO/DI. You can make it at home easily.

Just yesterday I tested PO4 in my coral quarantine tank FIVE TIMES. The results:

• 0.22 (vial wasn't clean probably)
• 0.06
• 0.18 (put fingers inside the pouch)
• 0.02
• 0.04

I'd totally get a different PO4 test if I wasn't terrible at distinguishing shades of colour.
You'll find plenty of threads saying the Hanna PO4 checker gives inconsistent readings.

Thank you, that's some good info, but I was getting very consistent readings between .03-.05 and am still getting consistent reading just much higher now. last 2 tests were .34 and .36

 

[gbru316]

Probably wouldn't hurt to test a reference standard to verify checker accuracy.

HI774 Phosphorous ULR standard
HI713 Phosphate Low Range Standard
HI736 Phosphorous Standard
HI717 Phosphate HR Standard

 

[EricR]

Thank you, that's some good info, but I was getting very consistent readings between .03-.05 and am still getting consistent reading just much higher now. last 2 tests were .34 and .36

That's a pretty massive trend swing. (((0.04ish is what I'd consider happy range vs 0.3x is way high)))

My LFS uses Milwaukee and my Hanna ULR is always roughly 0.02 lower on same sample ((("always" meaning the 3 times I've had LFS test same sample)))

 

[Davisc1293]

That's a pretty massive trend swing. (((0.04ish is what I'd consider happy range vs 0.3x is way high)))

My LFS uses Milwaukee and my Hanna ULR is always roughly 0.02 lower on same sample ((("always" meaning the 3 times I've had LFS test same sample)))

I've always found if very accurate, but been running a lot of phosgurd the last few hours tested again and its still increasing two more tests .39 and .4 as of right now

 

[Davisc1293]

Probably wouldn't hurt to test a reference standard to verify checker accuracy.

HI774 Phosphorous ULR standard
HI713 Phosphate Low Range Standard
HI736 Phosphorous Standard
HI717 Phosphate HR Standard

Just ordered some because it will be nice to confirm but like I said its been pretty consistent.

 

[WVNed]

Mine just did this. I cleaned the vials in some RODI and vinegar and they went back down.

 

[Davisc1293]

Mine just did this. I cleaned the vials in some RODI and vinegar and they went back down.

I tested multiple times with different cuvettes and keep the cuvettes clean and filled with rodi water when not being used. Im at a loss with this tank again.

 

[WVNed]

Mine were clean to my eye but apparently not clean enough.

 

[Blake423]

My salifert PO4 test kit asks for 10 ml water, seems a lot more than what's in this pic?

 

[Davisc1293]

My salifert PO4 test kit asks for 10 ml water, seems a lot more than what's in this pic?

this is my silicate test, i use the hanna checker for p04 i do also have salifert tests but find it very hard to read.

 

[gbroadbridge]

The test is probably accurate, and yes it can rise to that level quickly.
If you test some freshly mixed salt water and get a reading of 0.03 or under I'd say the tester is fine.

 

[undermind]

this is my silicate test, i use the hanna checker for p04 i do also have salifert tests but find it very hard to read.

I was confused by this also because the vial is in front of a salifert po4 test.

How long of a time period has passed between being around 0.04 and now where it's testing high?

 

[Davisc1293]

I wouldnt say overnight by any means but verry fast. days not weeks. The red circles are me trying to pick a color on the salifert test the rest are from a hanna checker. Before this ive never seen my po4 above .11 but usually sits around .04-.06. But i did stop testing daily on the 17th when i got my first high reading and thought the silicates i was dosing could be causing a false high reading.

 

[Randy Holmes-Farley Verified Community Expert]

This thread discusses interference:

High Silica interference with PO4 measurement

Tip to @Jason mack who brought it up earlier in a dino thread. I was skeptical, but it seems to be true, and in some cases, it might change how we choose to dose and test etc. This is a combo of data from me and @Rick Mathew Saltwater spiked with different levels of Silica was measured for...

www.reef2reef.com

 

[Davisc1293]

This thread discusses interference:

High Silica interference with PO4 measurement

Tip to @Jason mack who brought it up earlier in a dino thread. I was skeptical, but it seems to be true, and in some cases, it might change how we choose to dose and test etc. This is a combo of data from me and @Rick Mathew Saltwater spiked with different levels of Silica was measured for...

www.reef2reef.com

Thank you, Looking at that graph and and seeing my salifert test test only showing about 1ppm of si would you trust the hanna checker being almost .4 or would you think the si test is off?