I'll share an interesting lip locking story.
I have 2m3f Guianacara in a 125g tank. Originally, one male was a lot larger, but over time the smaller male has started to catch up. I never had any aggression in the group, beyond an occasional nip or when the pair was guarding offspring. One day I noticed the two males were flaring at each other, after a few minutes of flaring they lip locked! They literally went at it for at least 30-45 minutes! Finally, the sub male let go and backed up from the dominate male. After he let go, there was some chasing and the whole ordeal was over. There were marks right above the lips (is that anatomically correct?) on both fish, but no evidence of the scuffle anywhere else. I have not witnessed any aggression since then, and both males will swim in close proximity to each other.
So in a nutshell, that is my idea of lip locking.
Wow. That is a really long lip lock. The longest I have witnessed from my fish were only a few minutes long. I would imagine there would be a little damage to the mouth area after such a long hold with both fish tugging back and forth. You've got some stubborn males there. LOL
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