Aggresive Rainbow Cichlid?

[mark1980]

Hi, I have a newly set up tank (1 week ago). The tank is a large 330ltr corner tank.
On setting up my tank I added some mature media to the filter and 4 rainbow cichlids.
I have been testing the water daily, no traces of ammonia or nitrite so today I have added a britlenose plec.
The Rainbows have been swimming about and feeding together in harmony all week. Today though I'm surprised to see that one of the rainbows which is slightly larger than the other 3 is constantly chasing the others around the tank appearing to be aggresive. I wasn't expecting this and wondered if I could just have a bad tempered one or there could be another reason for this, Mark.

 

[rdp50734]

Possibly just showing who is boss! It should calm down soon!

 

[Monty-2010]

Is he chasing them all is he leaving any one of them in particular alone? try re arranging some of the decor in the tank or if it gets too much take him out for a little bit and put him back in that should calm him down

 

[mark1980]

He was attacking all 3 but he seems to have calmed down now. Will keep monitoring, thanks