Quote Originally Posted by stinkyattic
Not mold, it's salt! I've seen that commonly on coco and rapidrooters even- you actually get salt crystals building up as the nute solution evaporates off exposed bits!
Feel it... a bit hard? Crunchy, even?
No, it's not salt. I *do* have salt on some of the clay pebbles in the other pots, especially around the edges. This is definitely mold - long hairy fibers, not crystals. It's soft and slimy to the touch.