What's wrong w/ my clam??

[kawasaki]

Have had him for a long time and has grown like crazy but started acting wierd about 4 days ago. He was completely closed on and off for 3 days then opened up yesterday but his incurrent siphon was gaping (went back to normal) and excurrent is still all closed up. And he looks all puckered through the middle (see Pic) Went to pick him up to have a look for snails and he wouldn't even close up. No snails or obvious predators that I can see. The only change has been phasing in a new salt 1 month ago, from RC to Oceanic.

Perams:

75 gal
150watt MH Sunpod + 2 T5's
SG 1.025
Temp 78
PH 8.0 was 8.3 last week.
Cal 420
Alk dKH 7.5 was 8.9 before new salt.
Ammonia, Nitrate, Nitrites, Phosphates - 0

 

[kawasaki]

FYI You can't really tell in the picture but the middle is really stretched out and puckered. What would cause it to do that?

 

[a4twenty]

why the pH swing?

your alk is getting a little low, can you correct it?

what are you using and how do you maintain Ca and Alk?? are you dosing anything else??

what fish and inverts do you have in the tank?

 

[quicksilverq]

wow your alk did change fast. Your tank is not that big eather I was told once that any changes will affect smaller tanks alot more than a larger one (every one should know that) and clams are really really sensitive. If I were you I would go back to that other salt and in a hurry would not want to lose such a nice clam. Your Ph was perfect why the change in salt's?

 

[clamdigs]

Squamosas that large tend to not really use their byssal organs (threads or plug) any more. I would be surprised if yours was attached by more then a thread or two. This sometimes leaves the byssal area wide open at times and grains of sand can get in there and irritate the lower organs - clams will pulse, open and close, then not close or not open because the sand may be rubbing a weird area. It happens to my Squamosas all the time and they usually just work through it; other then that it looks perfectly healthy.