PJ Cardinal

I have had a PJ Cardinal in my tank for about 9 months. I had 2 and one died. I never got another one until yesterday. He already killed the new one. I didn't think they were an aggressive fish. Know I am wondering if he has been the one killing the other fish in the tank.

 

my pj that i have had for about 6 mounths is very aggressive to my yellowtail damsel. i guess they just get aggressive over time.

 

Older ones can be aggressive, although I'm surprised it actually killed the new add. Are you sure the new one was healthy? Did you QT it?

 

I did not QT it. Pretty much as soon as I put it in the tank he was going after him. I have put other fish in before and he wanted nothing to do with them.

 

The reason I asked about QT, in addition to the fact that sick fish will be weaker, is that some fish will kill off sick fish in the school. I guess there must be a benefit such as possibly it helps keep disease from spreading. I'm not sure if that is true of PJs though. Could also be another male, although, PJs males tend not to be as aggressive towards each other as some cardinals. In the future, if that happens, one thing you can do is turn the lights off and let them acclimate. Also, definitely QTing will help, not only sort out disease, but get them eating and stronger after shipping/transfer.

 

OK so I thought my new PJ Cardinal was dead. A day after I first posted this, I saw him swimming around. But he just kinda lays in the corner and comes out every once in awhile. The older one will just hang out next to it. Not really sure what to do??????

 

Cardinals will be aggressive towards other cardinals unless you have a mated pair.

 

Thats kinda what I was thinking..

 

Let me tell you this guys become mean over time, I had a school of 7 and they fought with each other until 3 remained and every time I tried to introduce a few more they would go after them.