Easing aggression between fish

[atte]

I have a 29gal tank with a chromis, clownfish, and banggai cardinal. The clown has always "charged" at the chromis occasionally, but they used to swim around together just fine. Ever since I added the cardinal, the two have been chasing the chromis around and it just hides in a fake plant all day (other than at feeding time). I guess it's the cardinal that really scares it because the cardinal will really follow it around whereas the clown just kinda darts at it once or twice and then goes on its own way.

At first I thought of returning the chromis and getting something else, but what if the next fish meets the same fate? I don't think you can really predict how the two (cardinal mostly) would react to whatever fish I get. I also dont know if my LFS will take a sw fish back but I hope they will because I'm not asking for a refund or anything.

What would you suggest I do?

 

[melosu58]

Whenever aggression happens do two things. 1) Cut the lights off. 2) Move some of your rockwork around.

 

[HappyHooligan]

I returned an aggressive clown.

 

[atte]

I already had been shutting the lights off whenever this happened but by now the chromis is just scared and hides the whole day. I will try moving the rock around and even purchase some more base rock I think. If that doesn't work I'll see what to do.