Storing tank water for friend over night

[Visuals]

Just curious how long can I store tank water in a 5 gallon jug for? I plan to get a 2nd tank and wondered if it would be safe to use my old tank water that's been bottled up. Can I just reheat it and run a power head when I'm about to use it or is that water dead water?

I guess it would be like me buying ocean water? But just with my old water from my active tank?

 

[Fish Think Pink]

Just curious how long can I store tank water in a 5 gallon jug for? I plan to get a 2nd tank and wondered if it would be safe to use my old tank water that's been bottled up. Can I just reheat it and run a power head when I'm about to use it or is that water dead water?

I guess it would be like me buying ocean water? But just with my old water from my active tank?

"old tank water" as in comes from old tank that had biologics in it?

If so, how long would you leave out a tuna sandwich before eating it. Probably go a little longer (2-3x) than whatever you answer is to that question.

If you are talking filtered water mixed with salt (nothing in it, but also no chlorine to prevent mold because it was filtered water...), then likely can go a long time but just take chances with mold IF mold grows

 

[Visuals]

"old tank water" as in comes from old tank that had biologics in it?

If so, how long would you leave out a tuna sandwich before eating it. Probably go a little longer (2-3x) than whatever you answer is to that question.

If you are talking filtered water mixed with salt (nothing in it, but also no chlorine to prevent mold because it was filtered water...), then likely can go a long time but just take chances with mold IF mold grows

Yeah, I was thinking of old tank water that I pulled from an established tank. Just curious if this is similar to say ocean water from lfs, since that stuff is also sitting around? Just curious if it's ok to leave it for a day and use it?