It has a lot to do with the wattage of the bulb, but also how strong the bulb is. It matters more on how much light the bulb produces into the tank (it's been a long day and I can't remember the technical term for this right now). For example, my 10K T5HO 39watt bulbs made by Current did not produce even half the light that I get from my Coralife 10K T5HO 39watt bulbs on the same fixture. Another factor is whether your light has reflectors or not and if they're individual or not (which is hard to find on most PC fixtures).
Anyways, since it's coming from a metal halide, you may have a little more difficulty with it. That being said, it can be done under PC's, it's just harder. Since it's a baby, you may have better luck.
It's going to need to be closer to the top of your rock work. More than likely it will move around until it finds a place to call home. If you allow it to do this, you'll have better luck.
Another factor to consider is whether or not you have fish or an anemone crab. My clowns beat the snots out of my anemones. The RBTA was very, very unhappy about this in the beginning and moved all over my tank and closed up for days and hid under a rock. It's bounced back and is beautiful. So if you have clowns, keep an eye on it while it's acclimating.
How big of an anemone is it?
If you have clowns, they may feed it for you, then you won't have to worry about that part. For the record, I do not feed any of my anemones anymore, just allow them to catch the floating left over fish food that I feed twice a day. They've actually been doing much better this way.
Good luck.