Green Star Polyp Rock,,,Dying?

[jpywell]

I just purchased a green star polyp covered rock. It was very healty and all polyps were open. When I put it in my tank they all opened up but gradually fewer and fewer polyps have been coming out. I have moved it a few times trying to find a spot it liked but haven't had any luck. I have tried placing it at the top and bottem of the tank and in direct water flow as well as out of the water flow completely. Can anyone suggest what I should try to save this? I had a polyp rock before and it didn't make it. Everyone says they are easy to keep but I must be doing something wrong.
My water parms are good, I have 2 400wt MH(7 hrs) and 2 55wt actinic PC (11hrs).
Please help me save this it's quite beautiful.

[MalHavoc]

What are your water parameters, exactly?

My colonies of GSP do best in vigorous current, with lots of light.

They are quite sensitive to old bulbs. How new are your light bulbs?

What sort of light were they under at the LFS? You have them under 400w bulbs, so they might be having a hard time acclimatizing. You may want to try putting them in a shaded area.

[Paul B]

That may be correct, I had a very large colony of them about a foot across, then they started dying. I changed my old VHO lamps and put in Metal Halide with power compacts and within 2 months they are growing and spreading again. Even some which I was sure were dead and were covered with algae revived.