Double posting because I tried my hand at making seared ahi tuna. The marinade I used was a garlic, ginger, soy sauce and sesame oil for about an hour and 15 minutes. I think I prefer my ahi to have a more neutral flavor. I might minus out the soy sauce next time and just do some salt. Also I learned that the minute sear is solid. I tried going over by about a minute on one side and it makes the fish hard to cut since it get flaky. So yeah, heat up your pan and go for a minute.
In the end though, $7 for 0.6 lbs*. I can do this every month or so to handle my fish craving which I just conquered for the next few weeks. This beats fish congee (Which is delicious but lacks the nature of tuna).
*With some refinements, I could just ignore the sushi places...