A trick I have used with several types of fish is the "bait and switch" method. Let them go hungry a few days and then feed some live crickets and a few floating pellets together to the fish, repeat that daily but never enough to fill up on, use fewer crickets and more pellets each day, After a week or two stop feeding crickets, If you want to switch to sinking pellets use the same kind of method to wean them off the floating ones. Except for a few obligate predators this method usually works, The marinade treatment would not hurt either.