Strange thing is i have found them to be more stable when stressed. For example, each time i have caught one and whilst chasing them around the tank with a net, they become more colourful. I returned the second Dat from the sump to the main tank last night. When i caught him he became stuck in the net. I ended up having to cut him free with scissors. Must have been stressful for the fish, but i have never seen him so colourful! He stayed like this for around 10 minutes in the main tank and then he went dark!