Was wondering if I could use them or if they wouldn't be hardy enough, I'd like to use 'em so I can be sure that there is no copper and for a welcome treat for my octo. Thanks again. :)

If you cycle with nitrex in your wet dry filter then the tank doesn't spike so badly (my peak was 1ppm ammonia) and the shrimps could survive.

Why not just use live rock though? Build all your caves and get everything set up and secure. Whatever you decide I would definitely use nitrex to help minimize the toxicity of the water.