I sold it by accident, I was clearing out my tanks and DOH!! I'm sure this has already been covered somewhere but I could not find it. Do I have to have him to reach the goal? He still shows in my trophy case.

You shouldn't need the fish to complete your goal. Once you've discovered a magical fish, that's it, that stat is there to stay.

The only way you would need that fish to complete the game is if you needed that breed to breed another magical fish.