I think one of my azure damsels has become the boss of the tank because whenever I add new damsels inside he'll pick on them till they die. He's the only damselfish in my 150 gallon right now and is healthy as ever. Was looking to try and get a shoal of them but I've pretty much given up and am looking to try my luck with blue green chromises instead. Will my azure damsel show any aggression towards the chromises?
It isn't clear to me what your end goal is so I'd like to get your take on that. Is it to add more damsels? Remove it and add something different? Or trap it, give it a time out, and re-introduce later?
You mentioned Chromis. Do you have a quarantine system setup and practiced in it? These fish are susceptible to Uronema. Do a search and you will see what I am talking about. Some hobbyist report that they will also fight it out until only one is left. Others say they have kept groups with success. Your mileage may vary but I want to stress the Uronema as if you don't quarantine you are risking introducing something that can take your your other fish.
Damsels again are one of those fish that will have members giving you varying opinions and experiences. You mentioned an Azure (Chrysiptera hemicyanea) which is in the Chrysiptera Genus. This Genus is one most damsel keepers recommend and for good reason. They are usually more calm so looking at damsels like the Allen, Tracey, Talbot, Springer, Rolland, Azure, etc. I know a member here had 50 to 60 damsels in his 450 gallon display some of which are Azure but I don't remember exactly.
@ca1ore was the member and if he is around can say how many and type.
One thing to note is that a lot of damsel keeping success, in my opinion, is having a properly setup display for what you are keeping. Damsels will readily pair up, spawn, and that is when trouble can happen. Having a properly setup system that allows enough rock work and coral colony growth helps give them separate living and spawning places. It also helps break the chase when things get a bit precarious. Places to sleep, retreat, spawn, and forage. Busy fish is one less prone to bother others.
I personally have 11 Biota Lyretail Damsels in my 210 gallon mixed reef. Several are spawning regularly and the display is peaceful. I do, however, have 4 large Biota Pink Square Anthias that keep them in check by randomly charging them throughout the day. This is a natural occurrence as I see it all the time when scuba diving over an Acropora reef crest. No fin damage just a charge, chase, and retreat thing then the damsels are back out doing their deal.
Prior to the Lyretails I had 7 Sapphire Damsels (Chrysiptera cyanea) and they are a bit more aggressive with fish around the nest. Existing fish knew about their spawning locations and times so it was peaceful. However trying to add any new fish was impossible be it lights out, acclimation box or mirror used. The new fish didn't know the lay out of the display or spawning locations so fights would happen and I'd have to remove the fish to prevent death. I rehomed them to a fellow hobbyist who had a larger system and was done adding fish. They are still going strong.
TL; DR: a lot of the challenges damsels bring is the environment and timing for which they are added. Chrysiptera Genus is typically recommended. Using an acclimation box also helps. Have a mitigation plan in place in case something doesn't go has planed. Your mileage may vary.
Edit: I should note that I am not saying you are not experienced in QT or practice it or don't know about Chromis and Uronema. I did not mean to sound like that or lecture. I was in a reply stream and didn't stop and after re-reading I thought to myself that could come across as negative and not my intent.
Example 1: Here is my display a few years back around 2021. I have 7 Sapphires, 1 Surge, and 1 Azure. They all coexisted:
Example 2: Here you can see the smaller Lyretails. They are black in body with yellow edges on the fins. There are 11 of these in the system currently.
