Stale saltwater

[lutz123]

While I know it's probably not great to use old tankwater (meaning sitting for two weeks with no heat/circulation) can someone tell me why? I don't mean dirty, yellow water - just water that has been sitting but isn't exactly clean either.

 

Is there an actual scientific reason, or is it just better safe than sorry?

Edited October 21, 2015 by lutz123

[YHSublime]

Two weeks isn't long, I've used it after sitting for two weeks in a sealed 5 gallon. I would just aerate it a bit and make sure your salinity is still where it should be.

 

No science from me, just personal experience and opinions here. 

[Origami]

No reason that I'm aware of why it can't be used for small water changes, Ashley. In terms of dissolved gasses, it should be in equilibrium with the environment, so that should be good. I'd give it a quick stir to ensure it's well mixed, though. Temperature-wise, you probably want to make sure that it's at or near your tank temperature before using it. Otherwise, you might have a big temperature swing.

 

Now, if there are any organics (dead bacterial films come to mind) in a deep reservoir, it's possible that water that sits unmixed for a long time be anoxic or anaerobic down deep and may have a bit of hydrogen sulfide in it. For this reason, it's probably better to run a pump a few times a day for several minutes to promote turnover and better oxygen distribution and exchange, or to run an air stone in the reservoir. In general, though, this is just a precaution for a situation where there are organics that can fuel decomposition. If you start with a clean container and new salt water, and there are no organics to speak of that can decay, you should be able to store usable salt water, unstirred for a long time without problem.

[WishNewFish]

The only other thing I could think about is, if the container is not clean, it could trigger growth of some algae and bacteria in that water - especially if you used that container for removing old tank water.

[lutz123]

Thanks. It was a little dirty and I ended up just making fresh.