SPECIES PROFILE: Discosoma spp.
Corallimorphs, mushrooms or just plain shrooms, these guys go by a lot of common names. Most of them are pretty similar in demands. Low to medium flow, low to medium light and good water quality. Some varieties can be kept under a couple of normal fluorescent bulbs, but they won't really show their true colors. If you have Metal Halides most will need to be kept low in the tank.
There is ongoing debate about what the genus name really should be. Some sources say Actinodiscus but some also say Discosoma. Whatever you
call them, they are a great beginner's coral and are about as easy as you
can get. Edit: since designing this page I've come to call these guys Discosoma, but I am too lazy to edit the illustrations. 
Discosoma sp. 2-16-07
Discosoma sp. 2-26-07
Discosoma sp. with Fromia milleporella 2-26-07
Discosoma sp. feeding 2-14-07
Discosoma sp. 2-20-07