If you just moved the tig over to the new tank, it might still be stressed out. Also, weaning any kind of fish off of live food will take time. Be persistent with the choice of food you would like to feed it regularly and keep providing it with that particular food.
Leaving the lights off will help a little but if you have cover for the tig to hide under then you shouldn't worry about that.
Rubbing food in garlic will enhance a fishes appetite but its a bit too much trouble for the mess.
I would recommend turning up the heater to about 80* and keep trying to feed it every other day or so. Feed all your other fish normally and you might even see a feeding response when the tig smells the food in the water.