Some clams and muscles will breed in your tank, but not all species. I've never had it happen, usually it's freshwater species like the quagga mussel that breed not marine species.
If you really want to target feed, turn off the pumps, then target feed the phyto right next to them. Wait a few mintues then turn the pumps back on.
I've never had these little hitchikers survive long once you introduce other animals to the tank. Shrimp, fish, and crabs, will eat them.