Can a Euphelia keep Zoas and GSP in check?

About to build my first aqua scape and am planning to have two masses of rock connected by a sort of archway. Would it be possible to have one side dominated by GSP and the other side dominated by Zoas and a Euphelia in between to keep them apart? Would the Euphelia kills them or just stop them from spreading?

Also planning to have a Xenia on an island? How far do I need to make the island to stop it crossing over to the main rock