Don't waste your money on bitcoin. That is what financial advisors, many of whom are members of the CNBC Digital Financial Advisor Council, said on Friday in a response to a poll on the digital currency. "You should invest only the amount of money you feel comfortable putting in a garbage basket and setting on fire," said Stacy Francis, president and CEO of Francis Financial in New York City. Bitcoin has staged an unprecedented rally this year. The price of one coin reached almost $20,000 last week after starting the year at below $1,000. Bitcoin futures launched Sunday on the Cboe Futures Exchange. The digital currency has attracted interest from former Fortress hedge fund manager Michael Novogratz, who said bitcoin could reach $40,000 by the end of 2018. It has also drawn critics like JPMorgan Chase CEO Jamie Dimon, who in September called it a "fraud," and said last week, "I remain highly skeptical of it." Financial advisors also see potential trouble ahead.

I would treat bitcoin like a penny stock. If you have money to blow and it doesn't affect your current and future financial goals, then have fun and enjoy the ride. Jeff Rose Alliance Wealth Management

The advisors CNBC surveyed agreed that clients should not invest in bitcoin and that it could be a bubble. Further, most of those advisors said that clients should not invest in the digital currency under any circumstances. Bitcoin's recent ups and downs are particularly concerning, Francis said, after it dropped 25 percent over five days before climbing 18 percent in two days. "We don't like to see these type of whipsaw movements in our portfolios," Francis said. Other worries about investing in bitcoin include a lack of fraud protection or connection to a central bank, said Shannon Eusey, CEO of Beacon Pointe Advisors in Newport Beach, California. Confusion surrounding the digital currency isn't limited to just investors. Eusey recalled how one investment manager said to her, "'I seriously don't know what the difference is between bitcoin and those 'gold coins' you used to jump up and grab in Super Mario Bros.'"

Cathy Curtis, founder and investment advisor at Curtis Financial Planning in Oakland, California, said curiosity inspired her to make her own investment in bitcoin. She invested $200 through Coinbase.com, a website where investors can buy and sell digital currency including bitcoin, ethereum and litecoin. Her investment had climbed to $472 as of Friday. Curtis said she still wouldn't encourage her clients, many of whom are in their 50s and still working, to invest in bitcoin. "There's no way I would recommend people put money in this," Curtis said. "If you want to do it, go ahead, but don't put a lot in." Peter Mallouk, president and chief investment officer at Creative Planning in Leawood, Kansas, said he has fielded questions from his millionaire clients on bitcoin. "Most of the questions are, 'What's all the fuss about?'" he said.

You should invest only the amount of money you feel comfortable putting in a garbage basket and setting on fire. Stacy Francis Francis Financial