So are you saying that the Hanna is misleading me and should not be used. My sump has alot of those pineapple spong
No, strictly speaking, with just two tests and not testing against a standard you don't know which one is right. The link to Rish Ross' review of ICP tested against a known standard it can be off. I'm guessing you didn't take the water sample for ICP at the same time as you tested with your Hanna, so it's possible there was a change in the amount of PO4 in your system so it's possible the difference you're seeing is in part a function of time and biology, not a totally a difference in testers. A PO4 standard is available online and using it to test your Hanna would give you an idea of how accurate, or inaccurate it is.