Reminds me when I introduced new butterfly fish into my DT where I have a dastardly nasty yellow tang. Initially, he went after them all the time. But eventually he left them alone. However, I noticed that when the lights subsided to the dusk/dawn level, he would again bother them for a while. Now, a couple years later, he will still occasionally do a lunge or attempted tail slap at them when the lights dim down in the evening. So yes, dusk/dawn light does seem to bring out aggression in some fish.
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