i found this a few days ago might be helpful - this is how im treating mine.
Pinched Mantle Disease:
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Unfortunately, at this time no conclusive evidence for the cause of pinched mantle disease has been found. However, tridacnids can be plagued by a number of microorganisms, and the pinched mantle disease may be the result of an attack by an unidentified protozoan, according to Barry Neigut, owner of Clams Direct. Hopefully, a definitive answer will be found in the future.
Protozoans are a mixed bunch of single-celled organisms, and as is the case with bacteria, lots of these organisms occur in marine environments and can live in/on tridacnids. It seems that, in some cases, these protozoans that live with tridacnids are parasites that don't cause any serious trouble when present in low numbers, but when pinched mantle disease strikes, the end result is almost always death unless it is treated in a timely manner.
This condition causes the mantle's smooth, curving edges to be pinched and contorted. A specimen may look like it is doing its best to stretch out its thin mantle tissue, but the margins just won't extend fully the way they should. According to Neigut, it affects T. crocea most often, with the other species being more resistant, but not immune. And, it can spread to other clams at times and is nearly 100% fatal, usually within a week or two of the first signs. Very bad, indeed! Fortunately, an easy treatment actually works well: an affected clam is given a freshwater dip for approximately 30 minutes in freshwater of the same temperature and pH as the tank from which it came. The only other thing to do is to thoroughly shake the clam for a few minutes while it is submerged in the freshwater to make sure that the water makes its way into all areas of the clam's body and into the spaces between the mantle tissue and the shell.
More examples of pinched mantle disease.
If done correctly, it may take a clam a day or two to show any signs of recovery and re-extend its mantle, and maybe a couple more days to regain a completely normal appearance. This treatment is highly effective, and while it may be stressful, it shouldn't kill any clams that aren't already seriously compromised. It might sound hard to believe that a tridacnid can survive such a long period in freshwater, but you should note that in their natural habitat many live in very shallow water and often become exposed to air at low tide and can end up sitting in the rain for up to several hours before the tide comes back in. Dick Perrin, owner of Tropicorium, also told me a story about putting a few clams in a bucket of freshwater and actually forgetting about them for several hours, but they all survived, too. The pinched mantle condition is consistently fatal unless treated, so even if a freshwater dip is stressful to a clam, you've got nothing to lose by trying.
The freshwater dip works, but Neigut also experimented with the medication metronidazole, a drug usually employed to kill protozoan and bacterial infections in fishes, but apparently it can also treat clams. However, he did find that the clams temporarily lost their bright colors for some unknown reason. The colors reportedly came back eventually, but for a period of several days the clams looked very dull (but not bleached). Very strange, but thankfully it's only temporary.
In any case, metronidazole is readily available to hobbyists, and each product has its own usage instructions. I don't add any sort of drug directly to a reef tank unless there's no other option, whatsoever. However, its use in a quarantine tank, on the other hand, should pose little problem (other than the possible loss of color), and I should also mention that any drug should be inactivated by adding some bleach to the treatment tank after the treatment is finished, before the water is discarded. Again, pinched mantle is almost always fatal, so action of some sort must be taken if you expect a clam to survive, regardless of possible side effects.
sorry for long post-- dont know how to link.
