Problem With Chromis

[super7]

Hey I have four blue green chromis and one is really getting picked on. He has some missing finnage(nips here and there) and a gash along the top of his head. Wondering how to prevent infection and aggression. This is a reef tank that has been running for just under 2 months. The other fish are fine though, same with the snails,toadstool and zoos.

Thanks Super7

[niloc16]

what size tank do you have them in. i've heard of a school picking off a couple until they are at a size where they feel comfortable. maybe 4 is too many for your size tank? just a guess

[super7]

My tank is a 65 gallon. The store where I work at has the same size tank with way more fish so I thought maybe too few.
No clue
Thanks Super7

[justinl]

a 65 is too small to harbour any more than one chromis imo. theyll pick each other off until there is eventually only one left.

a fish store is a much different situation for any fish situation. in an lfs the tanks are so crowded that fish have so much competition that none of them can even establish any kind of territory. there is also the fact that oftentimes the fish arent left in the tank long enough to show any aggressive behaviour.

[Der_Iron_Chef]

I have two chromis in a 55G, but they do square off semi-regularly. I used to have 4. I'm not sure what you *can* do.

[seashells]

I had 4 in a 75...Three stuck together but the 4th was left out, an outcast of sorts. Anyway took 2 out & the all fot along.

[ed99]

I had the same problem- started with 7 chromis and ended up with 4 in a 92 gal. It seems if they are not threatened they will drop the schooling behaviour and become more territorial with each other. I have heard that adding a small damsel can add enough peskiness to the tank that the chromis will stay in a school but never tried that myself. There was a thread on this subject a little while ago, seems few people have success unless they have a large tank.