Crushing the flakes into a powder usually works. Eventually they will get hungry enough to eat anything, at which time they will eat the flakes......and like it!
1 Gallon Bowl - White/Purple Half Moon Betta
1.5 Gallon - Blue Veil Tail Betta
2.5 Gallon - Red/Blue Veil Tail Betta
2.5 Gallon - Pea Puffer
5.5 Gallon - RCS, Ghost Shrimp, Ember Tetras, Sparkling Gouramis, Bumble Bee Gobies
10 Gallon - Pure Black Bar Endlers
29 Gallon - Planted Community - Cherry Barbs, Neon Tetras, Various Cory Cats, Albino Bristlenose Pleco