A few days ago I noticed this purple patch here starting and just wondering if someone can confirm what it is? Tank is probably 6-7 months old and probably 5 months post-cycle and having critters in it. Haven't noticed any algae growth before this patch. Everywhere I read forums, articles etc say cyano is either blue-green or red, well to me this is neither but rather very purple. Going to try and suction it all now along with a water change right now, but my water conditions weren't really bad when I test them last night, only test that really registered at all was approx 10ppm (maybe a little higher but it wasn't as dark at 20ppm) of nitrate. I don't have any corals just 2 clowns, a shrimp and a sand-sifting star, who isn't sifting sand nearly as efficiently as I thought he would, and now I'm down to 1 (from 2) turbo snails.