We use "it" to refer to a single fish:
* "Look at that beautiful fish! It has amazing colors."
However, it's important to note that:
* Specific species of fish can have distinct genders, and we use "he" or "she" accordingly when we know the gender.
* In some contexts, fish can be personified, especially in stories or poems, and we might use "he" or "she" in these cases.
So, the gender of fish in English is complex and depends on the context!