"Morgen werde ich Fisch essen."
Übersetzung:Tomorrow I will eat fish.
As far as I know both versions are correct. That's what I found. Maybe it helps you:
"Expressions of time go at the end of a statement.
Definite expressions of time can also go at the beginning of the sentence if they are not the main focus in the sentence. If you are in doubt – put it at the end of the sentence – it is more likely to be right."