Maxima staying mostly closed

[SCReef'n]

Ive had this clam for over a year and up until this point has been bulletproof. For the past several days he’s been only partially open during the day and opening more at night. I haven’t made any changes to my light or flow settings. Parameters are:
Alk 8.1
Calcium 480
Mag 1350
Pho’s.05
Nitrates 1
Calcium is a little high and I’m trying to slowly lower it by reducing dosing. I run rowaphos and carbon.
Any thoughts on steps I can take to help him get back to fully opened?

 

[Uncle99]

I healthy clam in your posted water chemistry should not of course be closed. He needs to be open to feed through photosynthesis.
Check for apatasia on shell close to mantle.
Is there someone new you have added recently.
Is there someone who can sting him?
Is there someone who pick at his mantle?
I see maybe a small nem to the left, can he get at the clam?

 

[vetteguy53081]

These guys can be somewhat sensitive. Assure you meet the follwoing:

Alk not to exceed 9
Temp not to exceed 80
salinity not to exceed 1.025
CA not to exceed 440
Good light and moderate water flow
Nitrate < .04
Phosphate < .05

No presence of Pyramid snails on or around them
No little crab living within the shell

Pyramid:

 

[SCReef'n]

No recent additions. I’ve been closely watching his shell for pests and haven’t seem any signs of pyramid snails or aptasia

 

[SCReef'n]

So today he started to move. Yesterday I performed a large wc and changed carbon to try and help. Today I noticed when I got home from work that the clam has shifted positions and keeps shifting on his rock. He’s more open today than he’s been in a while so Im hoping the wc helped. Should I move him lower or just cross my fingers and keep holding my breath? He’s currently sitting at about 250-300 par and has been since I purchased him a year ago.