No, no chlorine as it might haze the plastic. The safest will be to use a 50/50 solution of white vinegar specially if calcium carbonate, salt or coralline has to be removed.
If it has scratches you want to remove this will also be the right time to do it. Look for Novus products to do so.
This will also a good time to inspect the tank for chips, cracks, crazzing or defective joints. If in the garage I would seat it on white foam as leveled as possible and fill it up completely and leave it for a week. If it will leak you want to find out early and in your garage, not in the middle of your carpeted living room and once you are done with the installation.
