why not just add hot water to ur current water? unless u r having some special fish like discus or breeding other whys its not nessary to keep water over night. Just bring them out freshly from tap at the same temperature as ur tank and treat it with water conditioner and you be fine.
It is best to get it as close to tank temperature as possible. With small water changes, you could probably go with straght cold water. I always get mine to within a couple of degrees of the tank, but I'm changing a lot of water.
I just take a jug full out the new water thats going in and heat it in the microwave and then put it back mix around and do it again and It only takes about 7-10 heats to get my water change adequate and thats a 20% on a 60 gallon UK.
i just feel the tempreture of my aquarium water, then run hot and cold water into a bucket until it feels roughly the same tempreture, then add my tapsafe and ph balance then in it goes, never had a tempreture problem with this method and i always get it pretty close
It shouldn't, as long as you are using warm, not boiling water. If you are adding heated water to a bucket of cold water, add the stress coat once the water in the bucket is the proper temperature.