i bought a 3.5" crocea clam on saturday and drip acclimated before adding it to my tank . i looked it over at the lfs , it appeared to be in good shape and reacted very quickly when they moved around it . all my tank perams are right on . i have two other clams in there for a year and they are doing quite well (1 larger crocea and 1 dersa growing fast) . i placed it on the sand bed and was planning to slowly bring it up the rockwork . the lfs used pc lighting and i run dual 250w mh's over a 75 . the first day in there the clowns would kick up sand and i noticed it would not close and cause the sand to fly off the way the other two clams do so i gently waved my hand over it to get the sand off . i did notice it was gaping a little and i could see sand right thru the bottom of it .the next morning it was not extending it's mantle very far so i tested to see if it was reactive and it is was . third day before lights on i notice my nasarrius snails picking at it , i know that it not a good sign . i chased the snails away and the clam was still reactive to my movement so i moved it up the rockwork away from the snails in the hopes in may be able to heal ( it closed up as i was moving it ). on day 4 (this morning ) it is still reactive but not extending past the shell . no snails or shrimp are having at it and it still smells good .i did look it over for pyramid snails at the first sign of decline and could not see anything .are they easily visible ? the clams coloration is still good . i think it was probably in decline when i purchased it. is there anything i can do to try to save it ? might a fw dip help ? any ideas what might be the problem ? my other clams have done so well that i am at a loss here , but sitting back and doing nothing is not an option . i think it is dying . is it too late ? i will be getting a camera this afternoon so i can post pics . was hoping for some advice before then though . thanks