I've come back from the dead! (Just kidding, I wasn't dead - just dead busy)
I found this in the filter media of Nero's tank - what IS this? It looks like slimy algae or moss. I touched it with my finger but it didn't really feel like anything. If I had to hazard a guess I would think it's from the light, but if that's the cause shouldn't Octo's tank have the same thing? His filter media looks absolutely normal.
Sorry for the horrid picture quality! My phone hates taking pictures right now.