Hi Andy. I keep mine with no substrate too. I don't worry about the dirty egg flats, but you can change them if you like. Glad your lizard finally figured it out.It seemed to take forever to get some eggs out of mine too. Mine were nearly adults when I got them. Then when I finally did see an egg case or two it seemed to take for ever to see any babies, then within a month or so, BOOM! Hundreds or thousands, all of a sudden. I've got so many now that my egg flats feel heavy with them. BTW, I found a couple of escapees that I can't explain. I guess they could have fallen off while I was messing with them and I didn't notice, but I ran some vaseline around the top of my bin anyway, just to be safe. This didn't happen until I had millions of babies in there.