It depends on which species of ghost shrimp you have. If you have the ones with pinchers then they will likely kill the rcs.
As far as guppies go
okay... guess test kit is a must!! thanks for the advice ^^
Can you post what make/model you have? And any pictures of it?
Probably about 2 weeks depending on the driving force getting water through it. You need that test kit now though to monitor the tank and help judge the