Stop using student loan money to buy cryptocurrencies.

That's the assessment from David Bach, founder of AE Wealth Management and panelist on TheStreet's Investing Strategies for Millennials roundtable.

"A lot of millennials are using student loans to buy cryptocurrencies," he said. "In 5 years, 90% of the cryptocurrencies out there will be worth zero."

That said, Bach thinks the underlying blockchain technology "is going to change everything."

Check out our entire millennial investing roundtable here.