In which country do you live in? If it's one with a tax framework on cryptocurrencies, you're safe to cash out some thousands, if you're willing to pay the tax. I don't believe there's a direct answer to your question, though. Usually, it's fine. You can call this capital appreciation (and it is, indeed) and you'll be fine.

I recommend you asking your local board for a bank that doesn't ask for further info, to have less troubles.