help

If you have a spare submersible heater, you can stick that in a large rubbermade container before you add the water to the main tank. But AFAIK (and someone please correct me if I'm wrong), if the water is room temperature, and you're not changing ALL the water, changing little bit of the water at a time shouldn't really freak out the fish. It should equalize fairly quickly.

Regards,
Yash

put your heater in and set-it to the right temp, also maybe add some ph buffer, if the ph is low. thats what i do

Just stick a submersible heater set to the correct temp into what ever you are using to store the water. Once your temp is correct then you can mix your salt into it to get the correct salinity/s.g. Just remember that salinity/s.g. is dependent on the temp of your water. Don't mix in buffer until you have tested your water after the salt is mixed in because you may not need it anymore.

As far as room temp water is concerned if your room temp is fairly close to your tank temp you should be fine. I just put a heater in my water because my room temp is 10-12 degrees lower than my tank temp.