YOU SAID:

i had to take my fish for a walk

INTO JAPANESE

魚を散歩に連れて行かなければなりませんでした

BACK INTO ENGLISH

I had to take the fish for a walk

INTO JAPANESE

私は散歩のために魚を連れて行かなければなりませんでした

BACK INTO ENGLISH

I had to take the fish for a walk