How do ? The best stuff in the world to rid a tank of aptasia is Aptasia-X.
I've used it a lot and it is indeed reef safe and kills aptasia in about 2 minutes.
The stuff is applied with a seringe directly on the things mantle... then watch them go bye-bye !
As far as starving aptasia... it'll never happen. These devils flourish in the dark; in the light; with or without food... depth charges dont kill 'em either.
Anyway, there was a video on YouTube about Aptasia-X... recommend you view it... along with a zillion other excelent reef videos.