Snails

It appears I cannot keep any snails or crabs alive. I know some will die off or get stuck and can't upright themselves. I bought 6 more today include one giant one the size of a golf ball thinking I might have better luck. I put them in the tank around noon today and they haven't moved an inch. I'm starting to think it's something to do with the water?? I tested the water and everything seemed normal.
ph 8.2temp 78 degrees0 ammonia0 nitrates0 nitirites10 dkh1.021 salinity
What am I missing?

 

I have not, nor do I really know anything about copper in the tank. Please advise.
 
snails are local, Petland in Iowa City.
This morning I fed my fish and none of the snails have moved a muscle (no pun intended). I'm assuming its only matter of time before they are doomed too. My tank is starting to look like a graveyard of shells.
What do I do??

 

iaJim: The tank is mine which had been dry for over 6 months prior to me setting it up saltwater. I had African cichlids in it before that. I don't have another tank so i don't have anywhere else to go with the snail or crabs. I know i have never used a copper treatment before. I got my live rock from liverockranch.com and cured it for about a month in a Rubbermaid. I kept it in the rubber maid until all the above tested measures were acceptable. I have never tested for copper. My fish appear to be doing fine, just the invertebrates that are suckin it up. I'm assuming I can just get a test kit for copper? How does copper affect my tank?

beckerj3: After Google searching snails I noticed my salinity was a tad low too. I am working to slowly increase it now.

 

mthomp: I don't recall treating for ich or any other illness when i had cichlids. I did not do a vinegar wash. I stored it in my attached garage where it is dry and temp controlled. I made sure it was 100% dry before I covered it up with plastic to keep it relatively dust free. I did store my drift wood, gravel, power filters, ect in the tank while it sat empty. I can't think of anything toxic that would have been in reach of leaching into the silicone? I did have biobags stored in there but the carbon were sealed in their original bags. I'm stumped. Why wouldn't my fish be feeling these affects too?

What is this copper thing all about?

 

I can't think of any reason why my copper would be so high but I'm going to pick up a copper testing kit after work to confirm. If it is high copper, how do I lower? Water change id assume. Another ways?

 

Thanks Bill. Right after my last post i remembered that the only recent change i've made to my tank was replacing some overflow plumbing. The best thing i could find for a drain was a metal-ish tub drain from ace hardware. I bet that's the corporate then! Again I'm going to run out for a copper tester for confirmation but thats the ONLY thing i've changed on my tank recently. I'm guessing its leeching off that small piece of metal and has accumulated over the last two weeks. Hopefully a large water change will help! I'll let everyone know how it turns out. Gosh I fee like a stupid n00b.

 

Well I thought they were just not moving because of the move but I think they died slowly? Not really sure. I acclimated them to the water for 15 mins probably before releasing them. I picked up a copper test and its reading at 0 ppm!! Its had to tell the difference so at max copper is 0.25ppm and thats being generous. WTF?!? Back to the drawing board.

Now what?!?

 

Man I really don't want to redo the over flow plumbing. Think if I let it cycle more and did lot of water changes that it would eventually correct itself our leach out? Or would you suggest just redoing the plumbing all together? I mean the fish are fine. Live rock appears fine. All my crabs are alive just don't appear to be as active. I really don't know wanna change it but if I absolutely have to I will. I'm not real handy with the plumbing. 
p.s. I'm loving my gurgle buster!!