The rock I have is not an absolute square but it is kinda squarish in shape and is about 5 inches by 4 inches, so it's kinda big, I got for $40. The worms go in so fast when something comes really close to it, but I squirt them with food anyway. I read that each of those brown nobby things (Porites) is an animal too, not just the tree part (worms). I have had them probably four months or so now and they have been doing fine. There is about 30 of the trees on it. They come in cool colors (black, blue, red, maroon, orange), I think it is neat how all the different colored trees are on one rock. Most of the reading I found in regards to the actual Christmas Tree Worms say to place in shady spots or under ledges; however, I also located information as Amcarrig mentioned on Porites, which is the SPS coral that the worms are hosting on. So, I have concluded that the worms want shade and the coral needs high lighting, lol, what a freak of nature! I guess, I will leave it towards the top of my tank and when the lights are on the coral will be happy and when the lights go off the worms will be happy, whatever works. At least towards the top my gobies aren't covering it in sand.
Thanks guys!
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Established October 2006
120g acrylic, 2-250w MH, 4-65w actinic, saddle & tomatoe clowns, naso & yellow tang, cleaner shrimp, LT & carpet anemone, deresa & crocea clam, green bubble, white bubble, christmas tree worms, green star/blue clove/yellow polyps, asst. zoas, mushrooms, frogspawn, brain coral, ricordias, toadstool leather, colt | 
