You need to do some serious reading before you think about adding any live stock to the tank.
What size tank and what filter are you using. You said you had rock and corals? What are they.. If you had corals I can't imagine there still alive after sitting in FW
for a few days.
Test kits do you have any? have you tested the water?
Never use HOT water ....You say the fish will mix the salt.. There should be no undissolved salt in a tank with fish, so you need to get this corrected. Adding a power head to help add flow to the tank sounds like a good idea at this time.
Read, read and read some more before adding any fish or inverts..
Start out slow, nothing happens fast in this hobby except for bad things.