Do Zoas randomly pop up?

They can become a pest if they spread (and they can spread quickly). From what I understand, they can overrun tanks as easily as aptaisia if given a good foothold.

However, I have two that have been in my tank from the beginning... They haven't spread yet,.so I haven't removed them. Plus, they're green like yours, so they don't look too bad.

IMO, its up to as to whether or not you remove them.

 

I'll keep an eye on it. Thanks for the input everyone!