Chuck's 150 Gallon Reef Project

[ricosuave]

Maybe its just picking up a miniscule trace amount and .01 is the smallest increment that it has.

[Gecko]

I think Ricosuave is onto something here. BTW what about the Hanna Nitrate meter, you don’t trust it?

[ChuckG]

I'm reading .01 phosphates with the brand new Hanna meter. I accepted that at first but then when everything I tested came out to .01 it has to make me wonder.

Hanna Nitrate photometer does not work in salt water.
The only Hanna meters that do work in salt water are: Dissolved Oxygen, Nitrite and Phosphate so the phosphate one was the only one worth getting.

[Gecko]

I’m sure you already did this if you could but is there a way to calibrate it?

[ChuckG]

No I haven't. It's brand new. As soon as I get a chance I'll have to find out if and how it can be calibrated.

[ChuckG]

The Hanna meter IS working properly. I didn't specifically call Hanna to see if there is a way to calibrate because "I think" you sort of calibrate it for each and every test.

You take your sample water and have the meter ZERO it (isn't this like calibrating it?).
Then you add the reagent and let the meter do its thing and it gives you a reading.

With some more tests under my belt I have come to the conclusion that it is working and working very accurately.

Originally I got a reading of .01 on both of my tanks as well as my RO/DI water. The RO/DI water came from my holding tank.

I have since tested someone else's tank and got a reading of 1.00 - ouch! Yes, he does have algae growing.

I tested fresh water coming directly out of the DI chamber of my water filter and finally got a reading of 0.00. Retested the water from my RO/DI holding tank and still get 0.01.
Just prior to a water change my tank water was reading 0.03. After a water change it was back down to 0.01.

Now comes the part I don't understand. I'm obviously using water that has 0.01 PO4 to mix my salt water. I just tested the salt water in my holding tank and get a reading of 0.00.

????????????

I think this is enough to convince me that the meter works and I was assuming that I'm getting a little bit of PO4 leaching from the plastics in my holding tanks but now that I get a zero reading on my salt water holding tank I don't know what to think.

[ricosuave]

I'm betting there is some residue on your hands(or gloves) that is inadvertently being transferred to the cuvet before testing. Do you use a clean/sterile cuvet each test?

[ChuckG]

Same cuvet, well rinsed with RO/DI water directly from DI chamber (0 PO4).

I get residue from somewhere EVERY time I test my RO/DI holding tank? Seems unlikely to me.

[Paramecium]

You are probably binding the PO4 into an insoluable form with one of the ingredients in the salt mix. Due to the PO4 being such a minute amount there would be enough "reagent" in the free radicals in the salt mix to bind it into an insoluable form and thus the reagent for the test probe cannot break it apart to measure the ionic difference for the phosphorus molecule.

[ChuckG]

Now there's one that makes sense.