Dreams featuring unusual physical traits, such as your boyfriend having "big fish eyes," can symbolize a variety of things. Fish often represent emotions, intuition, or deeper subconscious feelings. The fact that he didn't know about it until you pointed it out could suggest a few interpretations:

1. Awareness and Perception: This dream might reflect your feelings about awareness in your relationship. Perhaps you feel that there are aspects of your boyfriend's personality or behaviors that he is unaware of, and you play a role in helping him see these things.
2. Emotional Insight: Fish eyes might symbolize a need for deeper emotional connection or insight. You might be craving a more profound understanding between you both, or you could be highlighting the importance of looking beyond the surface in your relationship.
3. Symbol of Change: Big eyes could also represent a sense of surprise or shock. It may indicate that something in your relationship is changing, and you are becoming more aware of it, even if your boyfriend is not.

Consider reflecting on your current feelings about your relationship and whether there are aspects you wish to explore further. This dream could be encouraging you to communicate openly with your boyfriend about your perceptions and feelings.