Derasa clam question

[tdwright1971]

I have had this clam for almost a year under t5 lighting, during which time it has double in size. Three weeks ago we moved and now it resides in a 36 bow with 250 watt 14k halide on for 7 hrs a day. Its mantle is extended about two inches past its shell. It still has good coloring and is not gaping, Is this normal?

http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs101.snc4/35413_10150226654300414_838960413_13546640_6253231_n.jpg