When I cook fish, I do this:
Cook around 250-275
Take a piece of foil, fold it in half, bend up sides to make "baking sheet" look
Lightly coat fish with Olive Oil
Use favorite fish rub (Dizzy Pig Raging River is great)
Squeeze lemon/lime juice on fish
Add some Rosemary or Thyme sprigs
Use some Peach/Cherry/Apple/etc wood, cook till fish is flaky.
This works well with whole fish, fillets and steaks.
***Edit***
If I am grilling, I bump up to 325-350 and try to indirect cook still with wood chunks. Finish off over direct fire for 1 min before pulling it off.