Are you an European Union citizen or resident? If yes, when are you declaring your cryptocurrency profit?

1) Everytime I have a profit
2) If profit greater than e.g. 5,000 EUR
3) I don't declare profits

If 1), when do you this declaration? at the end of one year? every month?
If 3), did the tax office knocked your door to ask about the unusual deposits in your bank account?

Thanks!