I have two convicts male and female in a 55G tank with a pair of rainbows. The females always digging hole all over my tank. I flaten all the rock and she does it again. I heard of this as a breeding behavior but she never lays eggs. And the fact that the two convicts are always together swimming around like right on top of eachother. The two have been in the tank for about 5 months and have always added like a pair but have never fry. The males about 4 inches and the females about 2 inches. Does anyone have any comments? Thanks for all the help.