Puzzling Chromis Question

[Scott Campbell]

I've never kept any Chromis until purchasing nine blue green chromis roughly a year ago. I had thought they would swim together in a school. But that has never really happened. They largely just do their own thing in rough proximity to one another. They occasionally bicker but get along well for the most part. All are healthy and quite beautiful. I have enjoyed their presence in my tank.

My question - I absolutely know I have nine chromis. But 99% of the time there are only eight of them swimmng about. There are enough size and coloration differences that I know it is not the same fish that is hiding. As if there is a rotation where one fish from the group must always hide for reasons unknown to me. Like there is chromis treasure or a secret chromis fortress that must be guarded. I have far too much rockwork to know where the ninth fish is hiding. But it makes no sense to me. It is exceedingly rare even when I feed the tank to see all nine. Once or twice a week I can confirm all nine exist. The eight swimming about never appear skittish or frightened. And no other fish in the tank feels compelled to hide. Is this baffling behavior normal for these crazy fools?

 

[TangerineSpeedo]

The baffling part is after a year, you still have nine... Be blessed that you do. It is usually one just disappears till you only have one.

 

[reef605]

The baffling part is after a year, you still have nine... Be blessed that you do. It is usually one just disappears till you only have one.

I’m in this situation currently. Lose one every couple days. Rest of them are fine, rest of the tank is fine.

 

[VintageReefer]

Very unusual that you even still have 9. Lucky you!

Normally one from the group tends to be ostracized. It’s usually the smallest one. Then they are pestered until they die from stress, fear, or damage from attacks.

If you have a few smaller ones they might rotate whose odd man out and survival of the 9 could be due to it never being one that’s always singled out

How big is the tank?

 

[Scott Campbell]

Thank you! There is one Chromis clearly smaller than the other eight. Kind of the runt of the group. And that fish is occasionally the one hiding. But only occasionally. The tank is 210 gallons with a lot of hiding places. As I type this the smallest fish is out and about as one of the eight. I suspect your theory is true. It has become extremely rare now for me to see all nine out at once. I imagine I'm likely to lose one soon if the rotation strategy falls apart. It is strange behavior that they turn on one another like this.