I need help with measuring PO4

Delphinus · #1 10-07-2007, 06:41 AM

Yeah ... see my problem was that not only do the instructions say "mix gently" (and not give any indication for how long), Hanna technical support themselves told me not to dissolve the sample.

That advice was way off the mark, I should have trusted my instincts. Since last night I've done about 6 more tests and lo and behold .... consistent results. (Yay!)

surgeonfish · #2 10-07-2007, 07:51 PM

Just wondering what your final PO4 value was? I was using Salifert and Nutrafin and having problems interpreting the results. I then bought the Merck kit and thought my PO4 was somewhere between 0.015 and 0.03. The Hanna meter is showing 0.04 twice which may explain the recent increase in algae in the tank.

Delphinus · #3 10-07-2007, 08:39 PM

Looks like 0.04 for me too. I'm not sure what to think of this number, I was sort of expecting it to be higher and then I could say "aha! I need to do something about this." But .. I dunno now? I renewed my phosban anyhow, I'll see what it says over the next few days.

Have you tested your RO/DI? I want to try that and see what it says. Although, is it fair to expect 0.00 from RO/DI? I really don't know. Guess I should test my incoming tap water too.

fencer · #4 10-07-2007, 10:30 PM

The issue here seems to be is lack of repeatablity. You might want to talk to some of the chemical companies or water treatment companies for a Phosphate standard soln. Then you can see how far the kit is off. Also you might try making you own soln of PO4 of known concentration. Just thinking out loud.

Delphinus · #5 10-09-2007, 04:22 PM

... And I still am not really getting repeatable test results. Andrewsk, when you get your unit can you please get in touch with me? I would like to compare test results (we can test your water, my water, or both).

Surgeonfish, .. are you not noticing particulates floating in the vial if you only swirl for 60 seconds? Because I check my vial every time after 60 seconds and there's nowhere near complete dissolution of the powdered reagent. I have to swirl for a minimum of two minutes, or more, before I stop noticing particulates floating in the water.

At any rate, I'm now convinced that either my tank has wildly fluctuating PO4 levels (unlikely and implausible, but I'll accept that it's not impossible), or that either my test unit is defective or I have a bad lot of reagents (boy am I glad I bought 100 of them

).

Before I send the unit back to the vendor however I would REALLY like some confirmation. So if anyone can help me test some PO4 I would be grateful.

Or I guess I can spring for another $100 and buy a D-D test kit.

I love bludgeoning money for this hobby.

(Oh man I am so frustrated...)

I actually found an aquarium water testing service. You mail in a sample, they email you back a complete panel. Sort of like how if you have a water well you're supposed to get it tested if you drink the water, same sort of thing. I've emailed them for a quote plus a reference sample kit, we'll see how feasible this option is. Failing that I might even call around town to see if any of the chem labs are willing to do a panel for me... I'm sick and tired of not knowing the full story of what my tank phosphates are.

Delphinus · #6 10-09-2007, 04:32 PM

Incidentally I did a test on my RO/DI water and it came out as 0.01.

But I guess now that I've established that I can't express any confidence in the test results, it doesn't really matter. I might as well say that my RO/DI tested as elephant, it makes about as much sense.

fencer · #7 10-09-2007, 05:05 PM

Did you try asking the poeple at the city water treament plant or the waste treatment plants. For sure those guys test for phosphate