I've had a total of about 10 amanos spread across 3 or 4 tanks for a long time now. I knew they were low order breeders and always assumed they were getting pregnant and letting them all go, but in a way that I just couldn't see. I never noticed any berries or anything like that. Recently, I found my naughty betta pestering the two in his small tank (he's a little feisty, but is isolated because his fins got shredded in a community tank) so I moved those amanos into my 29g community where there were already 3 others.
Not long afterwards—maybe a couple weeks?—the spouse calls me into the room where this 29g is located saying something weird is going on. She was attracted because the white clouds were in midwater in a kind of swarm, which isn't typical behavior. On closer inspection, an amano was perched on a rock flinging these little, uh, things into the middle of the tank, which the white clouds found to be a very pleasant surprise dinner. And that, my friends, is how I first saw a pregnant amano. I am guessing that my preference for big amanos meant that I had an all-female cast of characters until I was stuck with some smaller ones as a LFS that had low stock, which became the pair that I just added to my 29g.
Now I see two others that are more obviously berried, even though they don't look so much like berries.