I'm pretty new to this, and have had a bout of dyno in the past that I overcame (had the dreaded double 0 with phos and nit). I notice recently some stuff showing up on my sandbed and did some manual removal. This time, my phos and nitrates are normal. I thought it was cyano from the look of it, but I got a cheap microscop and tried to take some pics. To me, it looks like Ostreopsis, but again, new to this hobby.