RO vs saltwater for storing

[MarkW19]

I'm going to store some water for emergencies in a tightly sealed plastic container.

Given the choice, would storing just RO water, or pre-mixed saltwater be better for storing for a couple of months?

Storing the saltwater would mean I could use the water a few hours sooner than if it had to be mixed - but would normal RO water keep better?

[reefrunner69]

More than likely the straight RO water would be the saferst, IMO. You would not have to worry about impacting SG with evaporation, or ph impact from sitting.

[MarkW19]

Cool, thanks

On a similar point - I mix the salt with my RO water for at least a day, then leave it for a couple of days (with a lid covering it), then when I go back to it it's often got little white debris bits in it - not sure what they are - any ideas?

[reefrunner69]

probably calcium or magnesium precipitation.

[MarkW19]

I thought I was getting all those out with my RO unit? :p

As they're in the water anyway, I guess if a bit gets into the main tank during the waterchange, it's not a problem?

[reefrunner69]

Well, if it's a reef tank your adding water that is imbalanced which could throw off the balance of the tank. The salt mix has CA and MG in it

[Nitrate]

When I first got started in SW I stored my mixed water in what I thought was a tightly sealed container. After a water change I lost 3 fish. Being a noob a waited a couple of weeks and added more fish and used water out of the same container for the next water change. Of course I lost all my fish again.
My container wasnt sealed and I was killing my fish with bacteria from the stored SW. Since that I NEVER store SW for more than a few days without using it.

Im not the sharpest tack in the box, so my experience wouldnt necessarily apply to you.

[MarkW19]

Thanks for the input guys - I guess I'll store RO water, rather than mixed saltwater, then