[I]@vrba wrote:[/I][quote="Firefish don't actually do well in multiples. They tend to be aggressive toward each other. Perhaps they are forming their cliques and the two that are hiding have been kicked off the island? With that said said:
I have not seen any information online to lead me to this. What I HAVE seen is divers den selling them in three's.... I did find reports of fighting/nipping when theres only 2. But at the same time some people don't have that issue. Also noted people with issues introducing one to there tank after a single firefish is already in there which seems to always end in fighting."]
I am one of the people that currently does not have that issue with two. Again, keeping my fingers crossed that it stays that way. You should do more research. Andrew posted a great link that you could check out. This is a very common problem with firefish. Chromis and bangaii cardinals are two others that in my experience behave the same way as far as multiples are concerned.
It is certainly possible to have multiples. You could have a true pair or perhaps a few that manage to work out their hierarchy to the point of being ok in the same tank. My guess is that you are dealing with a hierarchy issue. Keep in mind the process of establishing their hierarchy can take weeks, months, or even a year or so. I have had chromis and cardinals do the same thing. Started with around five of each, never saw any fighting myself, but did see them ultimately separate in groups and then the groups got smaller. I now have two chromis that seem happy with each other and three cardinals. Two of the cardinals seem to be a pair or at least hang out together, and one stays on the other side of the tank. I would guess that it took 3-4 months for this to happen. During which everyone seemed cool with each other they simply just split off into groups and then their numbers started reducing.
With all of that said, I have seen tons of examples of the rules being broken in other members tanks and even on super trusted resources like divers den. Heck, come to think of it we all break the rules. If we didn't we would all have a huge tank with only one coral and one fish because this fish doesn't work with that fish and that fish doesn't work with that coral, etc. It's just good to know what to watch for when adding livestock to your tank so that at a minimum you are not stumped when the typical things happen.
Good luck with your firefish, I think they are absolutely beautiful especially in multiples. That's exactly why I got two of them recently. I would have got more, but didn't want to spend the money when I know that over time I would be down a few more than I bought.
