I have bred Jack Dempsey's in a thirty gallon tank. I bought them as a pair and within a week they laid eggs on a very small pile of rocks. The bottom was just normal gravel and I had a few pieces of driftwood. Most of the tank was just piles of small rocks. They laid the eggs on a round rock just smaller than a fist. I think they are easy to breed, but the hard part is getting the fish to pair off. Maybe try four females around the same size and see if they pair off with the two males. I didn't do anythhing special to the water, it just happened. I am trying to breed them again and I will let you know if I have any success. Good Luck!
Oh... make sure you have some hiding places or dither fish to make them feel safe. Mine seem to be VERY skittish.