It is not cyano
, I have had that in the past and this is very different. i just vacuumed most of it out so I don't have any good pics of it. Too busy this weekend to test (family visiting) but will try and do so on Monday.
BTW, a nutrient analyzer is a laboratory instrument that measures nutrients. It basically is a test kit, just a $60,000 one that is accurate to 2 decimal places at parts per billion for any of 5 nutrient parameters (nitrate, nitrite, ammonia, phosphate, silica).