Is this normal behavior?

[PoriferaBob]

Hey everyone! So this little green squamosa from the liveaquaria Divers Den has been with me for 13 days now. For the first few days he looked just like the blue one to the left with great mantle extention and fully opened. For about the last 8 or 9 though he has looked like this with just the tip of his mantle extended. All water params are SPS stable and in check. The lighting being used is a AI PRIME HD. they are in my frag tank however so they sit close to the light. I think par was around 150 last time i checked so intensity wouldn't be my first thought. Any ideas why this little guy isn't opening all the way? Blocked off from fish so thats ruled out, did find one Pyramid snail but removed it and gave him a little toothbrush scrub after. I haven't noticed any gaping taking place either. Just tucked in like the photo.

[AquaTDV]

Based on how well the Squamosa and Derasa look next to it. I would say your tank parameters are in check. Once clams are stressed other creatures will prey on them. Since you removed the possibility of it being fish. Check it out at night and make sure nassarius snails and bristle worms aren't getting to it. Or its possible it could be a light acclimation issue. Also when it was open was the mantle's color uniform and consistent throughout?

[PoriferaBob]

Hey AquaTDV! Thank you for your reply. Yes, the mantle coloration was normal. I didn't see any areas of bleaching or any thing out of the ordinary. I personally feel this has something do do with lighting. I know the par certainly is not high enough but I wonder if the light spectrum might be the issue. Too much white light possibly? Ive tried to dial back the white LED and increase the blues and violets. So far I have seen a VERY SUBTLE improvement. Being a green squamosa, would these light colors possibly be more "unnatural" to it? I know squamosa are found in deeper water then say a maxima, so there are less reds and whites penetrating down.

[Mirror Pond]

I'm pretty convinced that a lot of the captive bred clams available today are starving before we purchase them. From your pictures, there looks to be little to no new growth on the shell which has been my experience with several clams that I have lost lately. I'm not sure why so many seem to have little to no new shell growth when offered for sale since they obviously were growing before being offered for sale.