Not all urchins are reef safe, right? Are pencil urchins the only ones that are? Are they a bowl in a China closet about knocking corals over? I have some large snails that I've dubbed Turbo the terrible because of that!
Only put an urchin in a softy tank. They are bulldozers. Anyone want a flipper I will sell or swap mine. It is too weak on my 1/2 thick glass and I am used to a life time using razor blades and magnet pads.
Coralline grows fast in my tanks too. I have used the flipper scrapper too, works well but slow for me. I'm using a wider razor blade, available at hardware stores.