Is there anything that will save him

[bighead]

I have a dersa clam for around 6-7 months no problems at all looks great health everyday until my alk dropped from 7.8 to 6.2 in about a weeks time the alk stayed low for around a week when I was away from home I brought it back up to 7.8 over a couple of days my whole tank looks fine mostly sps but the clam is gaping and has no mantle extension and very slow reaction to lite changes is there anything I can do to help this clam it does not look to well to me

 

[Nina51]

gaping and no mantle extension are bad signs. i recently lost one that had been in my tank for 3+ years. no idea what happened, all of my parameters were perfect, saw no predation. what is your nitrate reading? high nitrates will cause problems with them. any pics?