As I said before - my problem have been that my Hanna HI-774 all the times report higher PO4 values that my Triton test do. It is a new meter bought in september last year. I wash my tubes with citric acid every two weeks. I calibrate two tubes to show the same zero value - using one for zero and one for the samples. after completed reaction time - I do a serie of tests with first zeroing (the zero sample) and than analysing (sample) I repeat this readings up to ten times. Mostly I get results that swing around an average value plus/minus 0,02 ppm. In the fall I read around 0,08 - 0.12 all the time. The corals did not grow very well. I run GFO and AL99 in attempts to pres it down to around 0.06 (my wanted value) Did not succeed - the Triton test that I send in in late august show 0.03 ppm PO4. I bought this Hanna in order to manage the PO4. When I start to test with it - I get 0.1 - 0.12. Try to press it down as I say above. In late november - next Triton show 0.018 ppm PO4. My Hanna show 0.1 ppm. Start to dose PO4. Corals start to grow and thing looks very much better. in late january - my Triton test show 0,036 and my Hanna show 0.12. I conclude that the Hanna show around 0.08 above my real PO4 content. Things have developed well and the last Triton (a week ago) show 0.06 ppm. My Hanna had run wild this time - I had forget to clean the tubes with acid. Exactly there I want to be.
A friend of mine have done a lot of testes with different brands and compared them with Triton tests. Surprisingly for me - he recommend Red Sea Pro PO4 test. And I know how meticulous and careful he is with everything he does - I decided to buy such a test. Today I get it and I did a comparison with this test and my Hanna (with acid cleaned tubes) and the result was rather thoughtful. Red sea 0.08 and an average of 6 readings (with the same sample and same zero sample) with Hanna give me 0.16 ppm. This was the first analyse I did with Red Sea Pro PO4 and I know of experiences that I need 15 - 20 tests in order to learn the methods I do for the first time. We will see in a week or two if I can trust this test instead of Hanna.
I can see another advantage with this test. I have to compare colours with my own eyes and in different lights (they recommend 6500 K) I know that my eyes can trick me and understand that the value is somewhere around the value I read. When I read the digits in the Hanna window - my brain trick me to think that this is the very real value because it is digits - not colours.
Sincerely Lasse
. Keep up the great work and be well, my friend!
