clam trouble

[Mike-fish]

parameters are:
temp 81
salinity 1.021
no3- 1
NO2- 0
NH3 -0
CA2+ - 486
ALK - 142
PO4 - 2.5
MG - unknown

lighting i s3x400w MH@14000k (old bulbs)
tank is 175g bow front
clam is on sand bed
checked yesterday for bristle worms few - removed
something odd foot was not deployed
tank mates:
powder blue tang
one spot foxface
copper band
1-2 chromis
clown
several shrimps

looked up pyramid snails haven't seen any