In this guide, I will show you how to change the default crontab editor.
If you want to specify an editor when opening the crontab file. And not just use the default for your system. You need to use VISUAL environment variable.
For a one time edit, launch the terminal and type:
EDITOR=nano crontab -e
If you want to make it permanent, you can put this line in your bash files.
nano ~/.bash_profile
and paste the line:
alias crontab='EDITOR=nano /usr/bin/crontab'
You can use any editor if want, like nano, mcedit, gedit, etc.
Note: to apply changes you should start a new session.