curing LR

[Dolf]

I have 50 Lbs of LR arriving Wed and none of it is cured. I know if I add it to the tank directly I will have a problem with an amonia spike and that I need to add it to a seperate container of salt water for a few days. I was wondering if this may not kill off some of the "critters" which are beneficial though? The tank is established and I do not run a skimmer. Any thoughts?
Also, I would like to keep a mantis shrimp and would like to set up a 15Gal for him. Any ideas where I can buy one of these "pests?"
Thanks.