I know most of experienced reefers already know about the three kinds of zoas (zoa, paly and protopaly) but still thought about sharing this article for those who don't know:
http://www.saltyunderground.com/arti...articles_id=52
I myself thought there's just two types: zoas and palys. And also had a misconception that zoas grow on mat and palys don't but I was wrong. Zoas and palys both grow on mat but protopalys don't. Great reading
