Citadel's Ken Griffin is not a fan of digital currencies and bitcoin. "I don’t have a single portfolio manager [of mine] who has told me we should buy bitcoin, not a single portfolio manager," he said at the Delivering Alpha Conference in New York on Wednesday. "I have a hard time finding myself wanting to be in a position for being a liquidity provider for a product I don’t believe in." The investor said he wishes the younger generation would focus on more productive activities than invest in digital currencies. "I still scratch my head" about bitcoin, he added. Griffin founded Citadel in 1990. The investor has a net worth of $9 billion, according to Forbes. His hedge fund firm now manages more than $30 billion in assets. Also in its role as a market maker, one out of every five US stocks trade through Citadel Securities on a daily basis, Griffin confirmed. The firm’s multistrategy fund, known as Wellington, was up 1.52 percent in June and 8.79 percent during the first half of the year. » Subscribe to CNBC: http://cnb.cx/SubscribeCNBC About CNBC: From 'Wall Street' to 'Main Street' to award winning original documentaries and Reality TV series, CNBC has you covered. Experience special sneak peeks of your favorite shows, exclusive video and more. Connect with CNBC News Online Get the latest news: http://www.cnbc.com/ Find CNBC News on Facebook: http://cnb.cx/LikeCNBC Follow CNBC News on Twitter: http://cnb.cx/FollowCNBC Follow CNBC News on Google+: http://cnb.cx/PlusCNBC Follow CNBC News on Instagram: http://cnb.cx/InstagramCNBC Hedge Fund Billionaire Griffin Knocks Bitcoin | CNBC