No bet on the aptasia.
Every fish is different.
I would be willing to bet a feather duster would be gone before the CB!
My tanks have always had 1 or 2 small aptasia that I kill with Aptasia X.
The CB never showed any interest that I noticed.
I did catch him several times eating my dusters till I pulled them all.
By then he would eat frozen and munch on bugs/worms in LR
and sub.(constant feeder for real).