Copper is present in NSW, you'll have to post a value to identify whether your range is out of the norm.
Copper is also extremely toxic to most inverts.
What size of clams and types of clams have your tried in the past?
It's hard to say what the levels were. Triton showed 4.20 ug/l copper which I believe equates to .0042 ppm... Prior to sending that sample I had done 3 30g water changes and a 60g water change within a weeks time. This was on a 260g system. I later found my new water was yielding 2.10 ug/l of copper iirc due to bad ro/di filters. If you can work those numbers back your better than I am.
As far as types and sizes I've tried derasa squamosa maxima and Crocea all different sizes. My first was a 5 inch Crocea lasted about 6 months. Tried some squamosa and after they looked good for a couple months added a maxima from divers den and lost it right at the 2 week mark. Always over 2 inches on those. I had that happen 3 times from DD I think. Then tried a local maxima from reef club member it 2 about 3 inches. That late a few months thought maybe everything was good then tried an expensive ultra maxima that was 6 inches. Made it about 2 months. That one I even checked par at the LFS and it was under 160 par of LEDs. Watched it do well there for 2 months before I bought it. Made a spot in my tank for it under the same par, I have reef breeders LEDs. I could be out of order on some of those but I tried about a dozen or so clams within a years time all with the same fate. Meanwhile watching my brother keep 3 for over a year and he has same lights but garbage water. He can't even keep Monti or birds nest that whole time yet I have a little of everything under solid conditions and can't keep a clam happy.
It is possible that the clams may have starved to death in the 3-4 months if lighting and/or nutrients were insufficient; what type of clams, what lighting/placement, and what is the nutrient load of your system?
The first few I can't speak for, but after learning to check for new growth they all continued to show new growth. I did try some on the bottom, middle and even tried blasting one of the maxima with about 400 par. I did move that one up slowly too as I have a par meter and kept track. I also was dosing phyto whenever I had clams, as well as acropower or other Amino's/vitamins supplements. Even had some home made phyto room local reefers for a while.
The 1-2 month time frame is generally from lack of enough light. What is the lighting and ever check PAR? Over that time did they ever put on new shell growth?
Clams seem more sensitive to everything though!
Mostly started them out at about 100 par and had some get up to 300, one up at about 400. Didn't seem to matter.
Yup, new shell growth is a big question! If they did not grow, then they were never "fine" but if they were growing that is really strange...
Do you have any peppermint shrimp? I hada clam that looked fine then a couple months after I added some peppermint shrimp to contol some aptashia And they ate away at its foot.
I did have peppermint shrimp. Never saw them near the clams though.
About 100 reasons, 90 of which no one has yet figured out. Lots of books talk about "sudden" and unexplained clam death.
1) Predation - Snails/Starving Inverts (Lobsters or bad crabs mostly - most shrimp wont bother them)
2) Disease - Pinched Mantle or derivatives
3) Food source - Lack of light and/or lack of nutrients in the water. Even if a clam is blasted with light it still needs some nitrogen in the water and vise versa. They need both sources of food.
4) Acclimation - Clams naturally handle swings pretty well since they often live in areas that can be exposed to air during very low tides. They do not however do well with pH swings or alk swings.
No3 used to be lower than it is now. Used to be about 2ppm solid but now more like 10 to 15. Po4 about the same. Used to be under .1 but now is generally around .2 to .3
As far as pests I've done all the research on clam pests and never found any. I have a bunch of wrasses I think would knock out any pests anyway. Never saw any fish pick on the clams and they never closed up prior to gaping and dying.
