I need help with measuring PO4

Delphinus · #1 10-06-2007, 04:40 AM

Looking for someone in the Calgary area to help me...

I need someone who has a Merck or D-D PO4 test kit, or a Hanna PO4 photometer to help me test my PO4 levels.

Here's my issue ... I HAVE the Hanna PO4 photometer but I suspect it is defective as I cannot get any readings with any degree of consistency. Ie. the numbers are all over the map. For example, I just took three readings on the same tank water and got 0.12, 0.04, 0.26.

Just to eliminate the possibility of user error, I need someone who can help me establish what my water PO4 really is.

Anyone? Please?

andrewsk · #2 10-06-2007, 05:29 AM

I am getting my New Hanna any day now. Ill let you know when it comes in.

Should be Monday and we can do a comparison.

Delphinus · #3 10-06-2007, 05:33 AM

Awesome. It would be great to do a comparison because I feel like a blind guy trying to understand what an elephant looks like.

Delphinus · #4 10-06-2007, 06:13 AM

Ok word to the wise, I just got some help on RC and I'll share what I've learned ... the instructions just say "mix gently" and then put the sample in. My lesson learned is, mix gently for like 2-3 minutes and then still do the 3 minute timed read.

I had asked Hanna technical support whether there should be residual powder before the test, they said yes, but no, you don't want any. I thought that didn't make any sense but that's what's been having me chase my tail. If I let the reagent dissolve completely then I seem to get consistent results. (Yay!)

surgeonfish · #5 10-07-2007, 05:27 AM

I just got my Hanna meter Friday. Love it already. I have been shaking the sample fairly vigerously for 60 sec and then testing and so far seems to work well.

Delphinus · #6 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 · #7 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 · #8 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 · #9 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 · #10 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.