I've also seen those yellow/whitish balls pop up in my crested gecko tank. You can't really remove them like Kmc was trying to say but they've been here and there for about a month and a half and my gecko seems fine and I don't really care about the look too much. Just don't move substrates because then it will spread. I had some substrate that I grabbed while trying to change some isopod cultures and it spread to those and got pretty bad so I just tossed it out. There wasn't any isopods yet so it was fine.