Phosphate test kit

[Ruth]

I use Salifert for virtually all of my test and have always found them to be quite reliable............until now.
I usually test my phosphate about once a month and it it usually reads between 0.003 and 0.1 - one of the few Salifert test I have found to use colour strips that you have to match up.
Anyway I purchased a Hanna colorimeter to test for phosphates and just cracked it open today. Imagine my surprise when I got a reading of 0.23????? WTH - so I did both tests again and got the same results. Holy cow this is a huge difference. No wonder I am having trouble with SPS in this tank and have moved most of it out. I started this tank in October with fresh live rock and it is bare bottom. The only thing that I can think of that is adding PO4 to my tank is frozen mysis that I feed daily as my Moorish Idol loves it. I always thaw the little cubes on some paper towel and then add them to tank water before I feed. I am going to try rinsing them really well before I add and see if this starts to bring it down. Needless to say some large water changes coming up this week!