I have kept Heckel's in the past out of an interest in the species simply because I share the same last name. I never had them breed (trio of Blue Headed Heckel's from Jack Wattley 1996) but raised them successfully. I found they liked baby guppies fed to them when they reached the 4 inch size. They were much more difficult to feed. They certainly got even more finicky after I began feeding them live foods.
I kept them in a low light aquarium, 29 gallons, ph of 6, pure RO with discus trace and RO Right at 88 degrees Celcius. I was not experienced enough at breeding and had no real interest in breeding them at the time.
Anyhow, hope the feedback helps.....
Joseph