Pearlscales are a round body type fish. With this body type they sometimes swim like that. If he is eating well and active, he's okay. Here is a site that gives a little infor on them.http://www.networkcpr.com/goldfish/Types_of_goldfish.html
Be careful about overfeeding him, especially as he is a fancy. Tell your Dad golds are pigs and will eat till they pop! Feed him once or twice a day and what he can eat in a couple of mintues, no more.
Enjoy him...golds are my faves!