I have a horrible experience with 3 crabs in a Cichlid tank. They are truly escape artists. I did everything I could, including covering all holes with plastic screen mesh (the kind for screen doors), taking out all high plants, and moving all rock to below 5 inches below water level and I still found them taking a walk around my living room daily. There was no interaction between them and Cichlids, at all. Ironically, I finally put them in a tuperware container about 3" high with some water and rocks and they never even tried to get out. No more crabs for me.