teardrop clam failing to open

[husker1]

I have two clams in my tank for three plus months. My crocea sp? opens totally still. My teardrop mantle opens maybe half way for 3 weeks. I see no damage and mouth looks good. They both thrived from the minute i put in tank. No new fish. 70 + soft and hard corals all doing great. Any ideas. Someone said do freshwater drip. Had a limited flatworm problem on one hard coral and a few mushrooms treated conservatively.

 

[quicksilverq]

List your Paramaters/fish plz

 

[husker1]

Ph 8.4
nitrates 10
mg 1300
ca 450
phosphates less .5


lights VHO 760 watts in 150 gallon 8 months old
crocea near top
teardrop 2/3 up from bottom
still very secure on rock opens more but not totally at night

 

[a4twenty]

and your fish / inverts??

also a pic can really help.