Firemouth behaving strangely

I have a pair of Firemouth Cichlids which have started acting strangely
since the introduction of a new Firemouth just a few days ago. Since his
introduction, the old pair moved to a different location in the tank and
every time that the new guy swims by, one of the old ones swims up to him
and flares out his/her gills. Once the new guy passes by, the old fish
returns back to the chosen spot and starts shaking in the presence of
his/her "partner". I've never seen them do this before and I'm wondering if
this is normal display of dominance?

Feedback much appreciated.
Mariana
to contact me offlist type: grdengrl at optonline dot net