[jlm86]

So i have my 30G water container to have water changes with prepared water.

Should i leave all week long , or prepare the water right before changes?

 

[pack-rat]

I try to use my water as soon as I can after getting it ready and to the right temp. If you leave a container of water standing for a while it usually gets a film on top, which I think is bacteria and such. I try not to use the water if a film starts to form.

If your container is made of something like glass that will not leach anything into the water, and you keep it covered until used, I would expect it to stay in good shape for several days.