the small ones dont grow overly fast...their growth rate will vary depending on nutrients available to them....over time, you will be notincing a lot more of them no doubt...
I'd still risk it Tiki. I found that the little feather dusters come and go anyhow. No assuring that they'll stay around but lots of guaranteeing the aiptasia will.
I was blasting my manajo amenones with boiling water, and I have a lot of tiny feather dusters and they all survived just fine. They seemed to be pretty tolerant of the hot water.