Recently I had been having issues getting some consistent and, I believe, accurate readings with my Hanna HI736 Phosphorous Ultra Low Range Checker. Here are some tips to help ensure you do get the most accurate readings possible. First of all make sure the water sample is free of debris and the vials do not have any water on the outside. The vials also need to be wiped down with a micro fiber cloth, like one you would use to clean eye glasses, to make sure there are no finger prints on the outside. You should also do the following:
  • Make sure you don’t create bubbles by shaking the vials too much.
  • Avoid letting the sample with the reagent sit for too long in the vial before you put it in the meter. After adding the reagent shake the vial gently for two minutes and then put it in the meter right away. If it is reacting for more then two minutes you may get a higher reading since the reaction time is longer.
  • Don’t let the sample sit in the vial after the test is done. Discard it immediately as the vial might get stained and impact future tests.
  • When done with the test rinse the vials with RODI water and put the vials back in the test kit. Do not rinse with tap water.
  • After using the vials for a year replace them since they may get dirty or stained after a lot of use. Replacement vials only cost $8 so it is worth it.


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If you are looking for additional insights and information, please explore my many other reef tank and SPS related articles as well as my book, A ReefBum’s Guide To Keeping an SPS Reef Tank: A Blueprint For Success. And you can see all of my reef tank videos online now as well as my Live HD Webcam.


Happy reef keeping!