I think you should have returned the sick one if anything! Remember these anemones are extremely hard to have bounce back, it will take lots of TLC and time.. as you can see, it's white.. therefore it is bleached. Once H. Magnifica show signs of bleaching, they can be very hard to convince to bounce back if you will.
I really think you should do yourself a favour and return the sick one, and try a whole new species that does not require Metal Halides or HQI lighting.
I am sorry, this anemone just won't survive under these conditions long-term... with the bleaching already, you've got your work cut out for you.
Sorry to sound like a brat, but really... the chances of survival are LOW... really low. These are the facts, not just me being an arse.
The clowns at this point, are not helping the anemone... if anything, only making it worse. The anemone is almost completely bleached , there is little zooaxenthelle (sp) remaining.
If you insist on keeping it... get ready to fork out some cash for a lighting upgrade and try feeding this anemone finely chopped up silversides... anything meaty. If he accepts food and does not spit it out, continue feeding 2-3 times per day.
Good luck... you've definitely got your work cut out for you at this point
