The back of my tank is up against a wall and I do in fact want the zoas to cover the entirety of the back of glass. If they start going on the sides...i have a good quality scraper, superglue and a lot of frag plugs!!!I've seen this on a couple of tanks where the zoas grow on the glass a little. Is there any chance this turns into a giant mess and all the glass is covered or for that matter not to have them cover all the glass? I can see my tank from the back so would still want that. I guess scraping them off would be easy if push came to shove?