Had him for just over 9 months now, it is now showing its adult colouration and is quite big. No fish should cause a problem if it is kept well fed. Mine eats three time a day so thats why i maybe don't have a problem. The only things i have ever seen it eat is a strange worm that was pokeing out of a rock and those tiny starfish that sometimes appear on the glass. Boths are pests so the boxfish is doing a good job.