Should I use the word "raise" or "grow" for animals?
Solution 1:
One can draw a comparison between raising a pet and raising a child. You not only feed them, but spend quality time with them. Fish, on the other hand, aren't quite given quality time, and given the lack of context I assume the fish were grown in a fish farm, in which case you treat them like plants - feed them and wait for them to grow.
Solution 2:
You raise animals and grow plants.