I haven't gotten any Pohnpei Clams but all I can pass on is what I hear from others. Yes they are very beautiful clams that is for sure. Talking with a importer of clams, I have been told that they have worms in them. Again, I have no knowledge of that myself only want I have been told.
The more I think about clams, still think it is a good idea to place them in a Q-tank for a few weeks to make sure things are fine before placing in your display tank. That is what I do with all my newly arrived clams, I place them in holding tanks for 5-7 days before shipping as I think that most people would agree that if you are going to lose a calm that is not healthy, it will be within the time period. Now that is not to say that you must also have your water chemistry well within limits to keep them that way. IMO IME
Barry