Due to a bout of insomnia, i was recently awake LATE at night and witnessed some nocturnal behavior. We have had the pair of them going on four months now and things have gone VERY well with them. Saw the pistol shrimp swimming all over the tank, finally going into the tunnels and the goby chilling out on the sand bed and noticed that the goby was basically kicked out of the tunnels by the pistol. Is this a common occurrence, say when the pistol is moulting? Towards the end of the next day, all was well once again, but just curious.