I found that they did not bother blue pearls, but hunted CRS. I figure it is to do with the brighter colours. Or, it could be that I had more of the blue pearls, so did not notice if the odd one was knocked off.
I did not see the babies (I just saw the distended jaw while they were brooding) as I went on a winter holiday and all the fish were dead when I got back 3 weeks later. I made the mistake of putting my central heating on holiday mode while I was away, and the tanks heater could not maintain the tanks temp when the house was near freezing. Live and learn.
They are my favourite of all the fish I have kept to date (25 or so years), like you say they have amazing character.