Dendros are my favorite coral too, and I have thought about putting some in with my cuttles when they get older to see if they will avoid them or not. I dunno if I will though.
This
http://www.tonmo.com/forums/showthre...t=10133&page=7 is a great thread to learn more about O. Mercatoris. Dwhatley raised her babies from the egg and has compiled an extensive journal about them. I haven't followed it much, but I'm sure she wouldn't mind if you post asking when they reached maturity. They are currently 9 months I believe and are mating and showing signs of senescence. My guess would be between 4 and 6 months depending on how much they ate, but other factors play a role as well.