I found two ways that worked for getting rid of aptasia.

1. Pinned some Algae (I think it is called Spirula) down ontop of one till it moved out onto the algae, and then discarded both.

2. Placed two pieces of small rockwork that had nothing important on it in the fresh tank with hungry guppies. They think aptasia is yummy!

Haven't seen any in 3 months.

Just my two cents