I had a 29 gallon Bio Cube in my office for years and the zoanthids were just thrilled to be a part of the tank. I would start them on your sandbed and see how they look. I think they would tolerate a higher placement if that is where you want to put them, like midway up in the tank. As to the teeny greenish starfish, take a picture, we will identify it in a snap!
thanks for the input MyNemesis its good to hear you had luck with them in the same tank i think i want a few on the sandbed upfront and then some on the rocks mid-level so i guess ill be my own lil zoas experiment. So these guys are gonna munch on them hun.... I dont have a sump i guess i could bring them back to the LFS lol