I am in agreement with tim. I have been doing some comparisons between saltwater taken from key west, and synthetically produced Instant ocean by aquarium systems. I dont think the argument is what the synthetic does have, but what it dosent. There are plenty of differences, but i wouldnt be concerned with things in exponential ppm, but more like the absence of Molybdenium. I dont know much from a clam standpoint..as to what trace elements really make a difference in how well they prosper, im just lookin at it from water chemistry...and i think you should try to mimic their natural circumstances as much as possible, without goin overboard like me. One thing i have noticed with the help of some more experienced reefers...is that sometimes it is better to just leave it alone...and let nature take its course...our own little captive piece of nature that is. So maybe thats the solution...the clams were homesick?