Convict blenny/ Engineered gobby.

[Kimmy101]

Ok, here is my situation.

I have a convict blenny/ engineered gobby. We have had him/her for awhile. So, we have wanted to get him a partner because from what I have read, they are social fish and are not aggressive.

So 2 weeks ago, we bought one that is the same size as the one we have, but it doesn't have the adult markings like our other one. It still has the juvenile markings.

Our 1st one made his home on the right hand side of the tank under rocks. The new one found him under there, so, we were like, awesome! Well a few days later I seen the new one on the other side of the tank under rocks making his home ( tunnels ) Well, our old one found him under there a couple days ago and has been constantly going after him, his poor little tail is looking ruff. So I tossed him into our sump.

So, question is, if my convict/engineered is not aggressive and is social, why is it being so mean to the new one? Is it being territorial?

Thanks in advance!