I think I've had mine for quite a while now, but I'm not sure if they are actually 18 months old or not. They were already quite big when I got them at the LFS. I would say the darker one is about 7 inches long, the lighter colored one is perhaps an inch shorter (but I've had him/her for longer).
They are not very active, so I didn't get too many pictures of their underside. I hope this is good enough:
The left one is the one I refer to as the darker one, the right, lighter brown one I've had for a bit longer. DSC06099.jpg
This is the lighter brown one. DSC06101.jpg
Underside of the darker one. DSC06107.jpg
Underside of the lighter one. DSC05275.jpg
Are they picky about whom they pair up with? I've read that some fish are and even if you have a male and a female, that won't necessary guarantee that they "like" each other.
Rearing the little ones sounds like a full time job, not just for the parents but for you as well. It must be such a rewarding experience knowing you successfully bred them. Thank you for all the info. I like to google and research, but you are right, there isn't much info out there. Forums are sometimes the best source of information.
I am looking forward to seeing more pictures of the little ones!