White Lights Turn Off And Aggression Comes Out

mav3rick478

Premium Member
Here's the scenario, I have a 28 gallon bowfront tank. A month ago I got a Yellow Chrysus Wrasse, he is a model citizen getting along with his tankmates, Percula, Coral Beauty and PJ Cardinal. His only fault was after 2 weeks he would constantly attack the glass in the corner by where he buries himself and I think it was because of his reflection. Fast forward to April 3rd, as a birthday present my wife got me a Melanarus Wrasse, she was a little bigger than my Chrysus but not by much. They seemed to get along fine for a week without any issues.

Then one night a week ago I noticed while I was going to feed my Acans that my Melanarus would attack my Chrysus every once and a while, it was like I was watching Shark Week where the Great White shoots up from the depths and torpedoes a seal. This would keep going on for a bit then they would both bury themselves for the night after all my lights turned off. Next day while all the lights were on there was no signs of aggression at all but as soon as the white lights turned off my Melanarus would head for a cave and look up to torpedo his target.

On Monday night I was going to start a water change and noticed something on the ground, it was my Chrysus Wrasse, he was not moving and I did not hear anything earlier so I did not know how long he was out of the tank. I quickly put him back in, he sank to the bottom by where he buries himself. He was at first slowly breathing, then started really breathing hard and after about five minutes went and buried himself. Last night when I got home from work everyone was out swimming but my Chrysus Wrasse was not in good shape, his side fins were tattered and his tail looks like it is getting fin rot. All was somewhat good till the white lights went off again. My wife says its like prison, I was not totally amused although I did laugh.

So has anyone witnessed behavior like this?
 
You guys might be right, I do remember before getting the Melanarus that my Chrysus used to hang out in the cave (by where they bury themselves) when the whites went out. Hmmm maybe I need to convince my wife to let me get a bigger tank to keep the peace....

Thanks guys.

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I have observed this across a number of different fish over the years. Dusk is also when a lot of courtship and spawning behaviors naturally happen, which I think can also bring out a dominance/aggressive side. I think a lot of fish are just generally more feisty around dusk because of this.
 
My male Melanurus is a handsome beast and very intolerant of any other wrasse shaped fish I try to introduce. I think I'd have to go with something much bigger to even give the new fish a chance. For now I am happy with my one magnificent Melanurus.
 
bright lights (and using for long period during the day) will always increase aggression in aggressive fish, imho...
 
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