Angelfish Aggression(?)

[Allysox]

I've had my angelfish for about seven months. They've been together in a 36 gallon, 2-foot high aquarium. Up until this point, they've been living peacefully, only chasing each other around now and again. Other than that, they seemed okay with each other, swimming closely without getting nosey. Recently, I've noticed that one of them has gotten more dominant, chasing the other away and occasionally into hiding. I didn't think much of it at first, thinking it was a short, territory dispute. However, I agreed to keep my eye on them. I turned to them earlier today and noticed a bit of lip-locking and nipping near each other's faces. I can't tell the sex of them, and I don't know if this is a sign of aggression or if they are a potential pair. I'll be out of town for the next few days, so I can't monitor them for a while. Can I get opinions on this?

II'll add some photos attached and see if anyone could sex them? For reference, the yellow one is the aggressor.

 

[Aiken Drum]

Lip locking could either be a sign of the testing each other out for spawning or territorial aggression. My female started spawning after about a year with a male angelfish that had been in the tank about 6 months. I got both as juveniles about 6 months apart. So the age of your fish is right for starting spawning.

I would say if they still hang out together when they arent being aggressive to each other its mating, if they constantly keep apart and one is hiding then its probably territorial aggression.

Angelfish can be difficult to sex until they mature and pair up. The best way to tell is looking at the differences in the papilla tube, behind the ventral fins, but i cant see this in your photos.

 

[gilpi]

A 36 might not have enough space for two angels especially with one aggressive. Angels are a toss of the dice, I've had three in a 29 high without problems but then I recently had three in a 55 where one killed two. Also remember, angels are cichlids.