Angelfish Aggression(?)

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.

It sounds like they have matured (at least some have) and they are trying to find suitable partners.

Am I correct that there are only two angelfish here? This is likely to end badly, if the likely male has decided to patrol his territory (in a tank this small it will be the entire tank space) and if the other angelfish is a male, he will soon be dead. If it is a female, hard to say; this fish must select its mate and bond for success long-term. Any male/female "pair" may tolerate each other, may even spawn a few times, before it is game over. Or they might, if really lucky, bond.

Always hard to tell genders with angels but I think the black koi is male and your gold is female. Its not an exact science but some male angelfish have thicker ventral fins at the top next to the body and/or a thickening on the forehead. Can you get side on full body photos?

As the others have said they have probably come of age. You would be best off looking to get larger tank, at least 40 inches long and 18 inches tall would be a good starting point.

Wills

I had a similar experience with a 29g. Started with about six young angels, hoping to get a bonded pair and planning to rehome the rest as they outgrew the tank. Ended up keeping two males (probably) who seemed to get along. Before long, one began terrorizing the other, so away he went, too. The final one lived alone for several years before I tore down the tank and rehomed him, too. I think angels are happier in a group than solo, but it was my best alternative at that point.

I have a friend who keeps a group of angels in a very large (150g?) tank, and they all get along. When a pair spawns, the others can keep their distance. The lesson I learned is that keeping such a large, potentially aggressive fish in such a smallish tank is generally not a great idea.

Wills said:

Always hard to tell genders with angels but I think the black koi is male and your gold is female. Its not an exact science but some male angelfish have thicker ventral fins at the top next to the body and/or a thickening on the forehead. Can you get side on full body photos?

As the others have said they have probably come of age. You would be best off looking to get larger tank, at least 40 inches long and 18 inches tall would be a good starting point.

Wills

Click to expand...

We're heading home in a few days, so I'll be able to get a better picture of them then. Until then, we've been having a friend check up on them, and so far from what they've said, they seem to be okay.

I've had plans for moving them into a larger tank for a while, but pretty soon after we got them, we had plans for moving a bit aways. I decided to hold off getting a larger tank until then, but it should only be a week or two more. I'll definitely look into a tank that size or larger to see how they do in, thank you for the suggestion!