Seems like one important thing is forgotten in Joom!Fish 2.0, and that is translation of the menu in admin.
This would usually be done by a xx-XX.com_joomfish.menu.ini file in admins language folder, but it also seems like JText is missing for the JF menu.
You'll find a proposal for the English language file for JF menu attached, the rest is up to you to fix. Edit!
Just tested, and this language file is loaded, but not all strings was correct - so it's only partly translated on my site now. Edit 2!
Got it working, seems like nothing needs to be done in the Fish. Only including the language file, and translators can also include it in their packs already - and start using it.