Tuxedo urchin eat chaeto?
 

Ok so I really like tux urchins but can't keep one in my display as it's acrylic but if I kept one in the sump would it eat my chaeto?

I keep 3 tuxedos plus a rock boring urchin in my fuge to eat the hair algae off the sides. None of them touch the gracillaria or chaetomorphia so you should be fine.