I love these stories.
A while back some disease broke out in my tank so I moved the BN's into a tank I had just prepared for my new Betta. They decided that was a good time to breed so I left them in there. When the fry were big enough I cleared out the parents and caught about 10 fry, I was sure I got them all. I then vaccumed the tank and drained it till it was almost empty. Refilled it with cold tap water and started up the tank power again. To my surprise, the next morning when the water had cleared, there was a little baby Bristle Nose sucking on the glass.
Shows how tough BN's are!
Congrats on the fry, it's not too easy to breed barbs, is it?
Be thankful that you got some free fish!