Originally Posted by Amphitrite
Sounds like they're establishing their territory it could end up in one or both being hurt. I'd keep a very close eye on their behaviour. Are there plenty of hiding places/plants in the tank?
There are. I have a large sunken ship that acts as a cave. I have a large rock formation that is hollowed out that acts as a large cave. I have a sea anemone that is an arching rock formation and it serves as a covered spot in a back corner. And My main center coral piece, the base is like "M" shaped, so under neath it is like little over hangs.
99% of the time, They leave each other alone. I've only seen this behavior once. The tank sits right next to the couch and I'm constantly watching it as I sit and watch TV. The particular behavior I posted about originally was only observed that one day. The rest of the time, they swim in front of eachother, around each other, etc.
The only other thing I've seen other than that sequence of events, is occasionally one will pick up some speed towards the other the other will move away...and the pursuit ends. But it's hardly a pursuit. More like one tail thrust by one to get close, a tail thrust by the other to move away, and that's it.
If it is aggressive behavior, it sure is tame. Looks more like curiosity, or playfull aggression. But if it turns noticably more violent, I'll remove one, more than likely the gourami.