Good luck, I got my Marm 4 months ago and I still can't break her.
I starved her for six days, still would not look at anything that did not swim. I tried nightcrawlers, shrimp, pellets, bloodworms, red wigglers, krill. She turns her nose up to it. My Johanna and Xingu I
both eat other types of foods but they will not touch pellets either.
Try starving and pour out in front of Powerhead to resemble a fish swimming around.
I use feeders for her that are fed as well as any cichlid that I have.
I quarantine them for several weeks. Feed them with a variety of cichlid foods. I use fat head minnows, gold fish, and shiners,
I rotate the new feeders after quarantine to another 10 gal that has well fed and healthy feeders.
I never throw feeders directly into tank after purchasing them.