Adding new chromis

jdpeters · Nov 5, 2018

when I started my tank 2.5 years ago I did research but obviously not enough. One of the original fish in the tank was one blue green chromis. I know it’s common to but them in odd number groups. I bought two more yesterday to try to add and not surprising the existing one was beating the hell out of the two new ones. It’s lights out and they are alive and hiding. Any chance they will get over past indifference or will I be back down to the original soon enough? Anyone ever luck out? I’m home today I’m gonna try to feed all day to disperse

mort · Nov 5, 2018

Chromis form hierarchies built on dominance so it's normal for them to squabble. The biggest problem is you have a dominant individual that knows the territory and thinks it his. You might find aggression reduces but be prepared to step in as they can be pretty mean. A social acclimation box might have helped but I would just keep feeding regularly and see if they settle in.

I'm not sure where the famous odd number theory came from but the size of the group is the important thing as you have to try and dilute the aggression and prevent the weakest individual getting picked off. Some people succeed with green chromis but that's probably as there are more than one species and one behaves better than the others.
Good luck.

jdpeters · Nov 5, 2018

mort said:
Chromis form hierarchies built on dominance so it's normal for them to squabble. The biggest problem is you have a dominant individual that knows the territory and thinks it his. You might find aggression reduces but be prepared to step in as they can be pretty mean. A social acclimation box might have helped but I would just keep feeding regularly and see if they settle in.

I'm not sure where the famous odd number theory came from but the size of the group is the important thing as you have to try and dilute the aggression and prevent the weakest individual getting picked off. Some people succeed with green chromis but that's probably as there are more than one species and one behaves better than the others.
Good luck.

Thank you for your feeding back. I might try my netted box later if I notice the aggression has worsened

shred5 · Nov 5, 2018

In allot of cases blue/green Chromis will kill each other no matter what till there is one left.
It is not always the case but it happens pretty often. So adding two with an existing one will likely not end well.

jdpeters · Nov 5, 2018

I knew better I wanted more life at a cheap price tag. They aren’t allowed out of one side of the tank. Any chance they can live that way? They don’t seem to care about the new azure damsel

sfin52 · Nov 5, 2018

I've got five for almost four years. The trick is having more than a couple to spread the aggression around that. I would have added 4 to 5.

mort · Nov 5, 2018

jdpeters said:
I knew better I wanted more life at a cheap price tag. They aren’t allowed out of one side of the tank. Any chance they can live that way? They don’t seem to care about the new azure damsel

Its unlikely they will do well if they are left cowering in a corner. Your best bet might be to remove the aggressor and swap it for a few more smaller ones although you still risk them picking each other off in time.

acro-ed · Nov 5, 2018

I've chimed in on a few chromis threads before. I've got 13 of them and I think the key is to have a lot of hiding spaces and also have larger fish that "scare" them periodically. With only a couple or few of them it's almost inevitable that they will pick each other off until you have just the dominant one.

sfin52 · Nov 5, 2018

acro-ed said:
I've chimed in on a few chromis threads before. I've got 13 of them and I think the key is to have a lot of hiding spaces and also have larger fish that "scare" them periodically. With only a couple or few of them it's almost inevitable that they will pick each other off until you have just the dominant one.

Agree 5 or more is what I like. I had three two died in qt. Picked up four more and dropped them in after qt no issues. Adding four spread the agression around but haven't lost any. That was four yrs ago.

DangerDave · Nov 5, 2018

It’s all in the numbers. My original 7 Chromis are all still there, 10 anthias, and an assortment other fish seem to keep the aggression dispersed.

Terry Brown · Nov 5, 2018

I had 3 adults chromis and added 4 more recently. One of the adults bullied the heck out of the younger ones I added (they where about half the size of the original ones ).. After a few days, they seemed to work everything out. I did feed the Chromis very heavy for a few days, in my experience Chromis have big appetites . They now all swim together. I think the key was they had lots of hiding places , I added several new ones at the same time, and they had lots to eat. I think if I added just 1 or 2 the dominant one might have killed the younger chromis.

davocean · Nov 5, 2018

mort said:
Chromis form hierarchies built on dominance so it's normal for them to squabble. The biggest problem is you have a dominant individual that knows the territory and thinks it his. You might find aggression reduces but be prepared to step in as they can be pretty mean. A social acclimation box might have helped but I would just keep feeding regularly and see if they settle in.

I'm not sure where the famous odd number theory came from but the size of the group is the important thing as you have to try and dilute the aggression and prevent the weakest individual getting picked off. Some people succeed with green chromis but that's probably as there are more than one species and one behaves better than the others.
Good luck.

My thoughts exactly, and I too wonder where the odd even came into play.

My longest run w/ chromis were same 6 for 6 years, and only lost them from equipment failure.
After that I've had several other long term groupings in odd and even numbers w/out issues.

I think at this point though your existing may be an issue for newcomers if it's taken a territorial stance.

I always get my chromis young and small, add a group of 5 or more, possibly starting off w/ juvies has helped, can't say for sure, obviously as many seem split on experiences w/ them there is something we have not recognized yet in why the varied outcomes

Super Fly · Dec 11, 2018

initially 5 chromis were added to my tank, the biggest one killed off all. Months later I added few more and the one established chromis killed them all so once again I'm down to one. I believe there has to be a bully that'll pick on the chromis driving them to shoal for protection. Otherwise in a peaceful tank with plenty of food, they'll kill each other until only one remains.

PatW · Dec 12, 2018

I have had problems with green chromis and dispar anthias. I believe that even large numbers do not help in certain cases. The dominant fish can identify the weakling and concentrate on it. Once the weakling is dead, it goes for the next one in line until there is one or none left (the last one dies of loneliness after murdering its fellows).

I had a green chromis, Chromis viridis, do this. It is in my tank. I added 3 really small blue chromis, Chromis cyanis. The green chromis picks on the blues, but I don't think that it can tell them apart. So it does not single out a target for special treatment. So with the aggression spread around, the blue chromis do fine. Oddly enough, the blue chromis have a level of aggression but it is not murderous.