I haven't had a problem with my Blues yet, granted they have only been in there for 2 weeks. I have 5 blues and 5 scarlets and the blues all hang out together on top of one rock. Every now and then they dispears then return to the rock. They must not care for scarlets though because yesterday on of my scarlets scaled the rock and all the blues ran off. I have two scarlets that do not get a long I had to reach in the tank and seperate them the other day they were locked up and one was gong to die.