I did have nopox running. I stopped this about a week ago. The slime is only in the sump. No lighting in there. The slime sits on the surface of the water. You can gently gather it together and get it out in one big ball of snot. No smell and clear. If you are clumsy when cleaning it, it will break up and then get sucked in to everything. It clogs the skimmer in a few hours. Doesn’t seem to want to go away.