I found something cool, though I'm sure I'm not the first. It is essentially plastic gridwork. Like a screen of fairly substantial, white screen. It is used for needlework or embroidery of some sort and comes in smallish sheets, squares, circles found in craft stores. It's awesome, so far. It keeps everything but melanogaster or hydei inside and is easily cut to fit different enclosures also easy to clean. My Unicorns are hanging from it just as they do metal screen or coffee filters. Nobody's moulted on it yet, but I think it'll be fine. Love it.