definately. its got something to do with helping the stomach to digest other foods, as it contains lignin and lignin is required in their diet as an aid to helping their food to do so. (without going into the details of biology/chem). it is a must for royals. its a good decoration, and holey pieces give them shelter and somewhere to hide too. many royals come into shops, malnurished, and when they are tried to fed, if they cannot digest the food with lack of bogwood (or internal parasites) they dont live too long.
if its looking on the skinnyside, put it in a quarentine tank, bare, with a piece of bogwood for a retreat and for food, and use internal parasite med. but if you do you must dilute it heavily, as meds become very concentrated in the algae they graze on, and many royals are killed by this poisoning. provide with plenty of roughage ie vegetables like cucumber etc, it is highly beneficial. hope you raise a monster!