Shrimp killed by trace amount of tap water?

[cf21]

I had an uncycled 2 litre (1/2 gallon) jar set up for 9 super shrimps. Seller gave me some crushed coral from his tank to jumpstart the bacteria growth. Some shrimp keepers have been able to keep them successfully without cycling so I didn't think too much about it.
The water was mixed with Instant Ocean salt to about 1.012. The rocks were boiled with distilled water. I made the mistake of rinsing the sand with filtered tap water because I ran out of distilled water. I also dumped the sand back in without letting it dry.
The shrimps were then acclimated for around an hour and then transferred to the jar. They were doing fine the first 12 hours, even regaining their colour. But after around 20 hours they started dying off. I took the last remaining one and transferred it to a different jar where it lived for 3 extra days.
Is the tap water in wet sand the culprit? Could they have been killed by difference in salinity or something else?

[JHRequiem]

First off, I'm sorry for your loss. Don't get discouraged!

I'm no expert, but it sounds like there was a mineral in the tap water that killed your shrimp. A half gallon isn't a lot, so even trace amounts on your rock is a lot in comparison. If you're able, I'd run a parameter test on your jar before trying again just to be safe, or even start over. Wishing you the best!

[cf21]

Thank you for the condolences.
I dumped the water out and washed everything with distilled water. Currently in week 2 of the cycle and hope to add more in a month or two.

[dglidden]

I'm not going to claim one way or another in your case, but I know my tap water where I live is AWFUL. I discovered that I need to alternate with distilled water when I water my plants or the buildup from the tap water will kill them off. It's possible you have similarly terrible tap water.

[cf21]

I'm not sure. The tap water here is naturally soft and is generally safe to drink. Maybe the trace amounts of chloride or something else killed them. Since it's a 1/2 gal there's very little room for error.

[KiwiCordell]

From what I understand, tap water has minerals, chemicals and no salinity.
I always keep a stash for distilled water “just in case”.

[Mustafa]

Do you have a picture of your tank? Besides the fact that some crushed coral from another tank is not enough to instantly mature a tank (signs of algae is still the best indicator of a ready tank), you may have some decoration/substrate etc. that may be either organic (i.e. decaying releasing ammonia) or leeching chemicals.