Why do you think you are loosing them? Milles are some of the hardier acros in my experience. Lots of light and flow! Of all the acros I lost, milles resisted the strongest.....some are still hanging on
I got a great pink mille from Betamed (Damon), one of the shaggiest I had and had excellent polyp extension from day 1. Maybe contact him for a known winner. If that don't work, maybe need to take a closer look at what's going on. GL!