Avoid beefheart at all costs. Nearly all species of Geophagus and Satanoperca are unable to process that level/type of fat in beefheart. I don't fully understand the ins and outs of it, hopefully someone can enlighten us, but it's certainly not good for them.
In my experience they go mental for live/frozen bloodworm. They'll munch any kind of worm.. glass worm, microworms, etc. They'll also eat a decent quality sinking granular dry food. They don't eat large foods in the wild, they tend to eat large quantities of small foods, sifting through the sand to filter out micro organisms etc. Avoid "Cichlid Pellets", they'll struggle with them until they're 10" body length.