In all the years I've had mine they have never responded to flake. They are insectivores. I've never tried worms on them. They will eat other frozen preps but they don't eat it in the same way, I feed them those because that's what they want to eat. When I first got mine I tried all different stuff, I ended up going with BML because the response to it was absolutely amazing. Every time they it eat it is like they have never eaten before. This is the sole reason I still keep them, to watch them eat.
All other food seems of less interest. All dried food seems to drop to the floor with little or no concern for it.
They will eat daphnia and bloodworm, just some gets wasted.
That's 7 years experience on these fish, as far as I know they are all wild caught specimens and are naturally tuned to a particular diet. You may get lucky with persistence. I didn't try too hard.
I find out what my fish eat and feed them that food.
In any case good luck, that is just my knowledge so far.