I found that during the summer when the house was warmer my Jack Dempsey's spawned often and as the house cooled for winter they slowed down. I added a heater set at 80 and this immediately induced spawning again. As I have a large number of fry currently in a grow out tank I have reduced the heat again to 70 and have not had another spawn. Has also reduced the agression of the male with the lower temp. Good Luck.