Speaking of fish. What kind of fish and how are you grilling it?
I often sear tuna on a chimney starter.
Fill a chimney starter with coals (at least 3 quarters of the way) and newspaper on the bottom. Light the newspaper. Warning this is extremely hot and smoky so make sure it's in a safe place (I usually just put it on top of my gas grill). Come back in 10-15 minutes.
Prepare tuna (about 3/4 to 1 inch thickness). Salt and pepper both sides. Place black and white sesame seeds on a plate. Place the edges of the tuna on the plate so it gets coated with the sesame seeds. Make sure no seeds get on top or bottom of tuna.
Oil or spray small grill grate. Once coals are white hot (about 10-15 minutes since lighting newspaper) place grate on top of chimney starter. Wait 2 minutes for grate to get hot. Place tuna on top of grate. Wait between 15 and 20 seconds (depending on thickness of tuna). Flip. Wait another 15 to 20 seconds. Remove.
Slice and serve on bed of Arugula and truffle oil.