Help with yellow tail damsel

[nano reef]

And from now on, always research before purchasing any livestock (this includes corals and inverts!)

I realize this is a very old thread but if you did your research you would read tat yellow tail damsels are not aggressive and the least aggressive of the Damsels! I bought one yesterday that i have been seeing for a while at my lfs but heard that damsels were aggressive but after reading that it dosnt apply to this type I ended up buying him. He has been fine so far But is my first fish! I also bought him for his hardiness as I wasnt sure if I was cycled, even the LFs could tell but thought i was. I started with 40 lbs live rock plus 32 live marine pure ball in a 36 gallon, Have had 0 ammonia and nitrites and low nitrates, but dint want to rick moving my beloved fish in there until I knew for sure' I also added Bacteria starter. So far same readings!

 

[Firefenex]

Just sharing my personal experience. I've had a tank setup for 8 years even though its been an off an on hobby for me. I left to college and my parents just kept it running with a couple mushrooms. Well because of covid 19 they found themselves at home and wanting to get fish. The guy at the Lfs told them to get damsels because they are hardy and go well together. He didn't tell them how to acclimate fish for salinity properly so after temp acclimating them, my parents dropped in a yellow tail, a humbug, a domino and a green chromis. The chromis died shortly. When I finally came home because of coivd and remote learning I noticed that the yellow tail which is arguably the same side if not slightly smaller than the humbug was running the tank. He would nip at the domino and the humbug about once every 3 minutes or more if they were where he wanted to be. I also noted that the domino had a parasite but was unable to save it because it died the next day. That left only the humbug to deal with the yellowtail's aggression and that resulted in the humbug always being at the top 3 inches of my 40 gallon breeder.

After about 3 weeks of constantly hearing people say "you need more fish" and me telling them "no they are too aggressive to add anything else" I finally caved and decided I would pick up another damsel. A domino to replace the domino. This one was smaller than the other too and when it was finally acclimated, I can tell you I have never seen so much aggression in my life!!! The yellowtail did not let up for a milisecond and the humbug suddenly decided to match that aggression. I spent about an hour of having my girl friend protect the domino with a net. I was able to make a cage to hold the new guy and see if the others would adapt. When they realized they couldn't get to him they calmed down and went elsewhere but at that point I had given up because when the cage was gone the aggression would continue or the domino would be stuck with a 4 inch cube of living space away from the others. So I returned the domino.

About a month later (today), the yellowtail has nipped t the fins of the humbug causing visible damage. The humbug is currently in that previous makeshift cage gasping for air even though I've tested salinity, ammonia, nitrates, nitrites and ph 3 times with perfect water conditions.

I've found myself googling damselfish aggresion at least once a week every week since I've been home and I am completely sold on never allowing another damsel in any fish tank ever. They are beautiful fish and I am jealous of others success with them; but the idea of chancing whether another fish will live peacefully, die, or spend its life being chased and beaten by a damsel is not something I'm willing to test.