Berghia nudibranchs questions

Discovered I have two aptasia plants in my tank tonight. Who knows what I
can't see. Weird to because I haven't added anything in a long time they
must have been hiding.

I have found that Berghia Nudibranchs are the best for aptasia and I'd been
wanting a nudibranch anyway. The questions:

1) I've read aptasia is all they eat. What do I feed them if/when they
eradicate my aptasia?
2) I have a brittle star. Is it true that the brittle starfish will make a
meal of the Berghia?

I appreciate the input. I really prefer the Lettuce Nudibranch to the
Berghia but I need the Berghia's talents so that's the direction I'm going
(unless any of you have heard of Lettuce Nudibranch eating aptasia too?? )

Thanks for the time,

Bryan
www.geocities.com/bryg30 if you want set up details