I've heard cichlids can breed at 2" and I've persoanlly seen a yellow lab a bit smaller spit out 6 babies, so anything is possible when you put animals in a see through box...LOL.
The vibrations could mean a couple of different things. It depends on where in the tank he's at. If he's under a rock shelf of some sort, then he's trying to motion attention to a nearby female that may be spawning. This is how they attract females to their egg spots on their anal fins. It tricks the female thinking it's an egg, so she goes to put it in her mouth and that's when the males spray their spew to fertilize the eggs. This is so of all mouthbrooders which I do believe the acei is and THAT is true oral sex. LOL.
If he's swimming about out in the open, then he's most likely signalling his dominance to other males in the tank.
Oh...and though these guys will breed all year round, this is the time of year when spawning behavior seems to be at it's most heightened.
