Mixing water for water change

[Nick Steele]

Okay so two weeks ago I made water and did my water change. I had about 2-3 gallons left so I let it continue to sit and mix and today I need to make more water.

Would it be okay to add rodi on top of my premade water then add more salt or should I just dump the 2-3 gallons and make a brand new 6-7 gallons?

 

[Eggs]

Okay so two weeks ago I made water and did my water change. I had about 2-3 gallons left so I let it continue to sit and mix and today I need to make more water.

Would it be okay to add rodi on top of my premade water then add more salt....

I do this all the time, reuse leftover saltwater, add RODI and salt to get desired salinity.
Haven’t had any issues.

 

[Nick Steele]

Good to know

 

[Reefer of Oz]

From what I gather and in my limited experience it should be fine. As long as the water is circulating to maintain gas exchange, ideally covered and dark to reduce bacterial growth and kept at a reasonable temperature, a single batch lasts several weeks.
I mix in a 30gal container, topping off the difference with RO water, calculated salt, mix, circulate for 4 days at least, do water change, let remainder circulate at tank temp, do more water changes until nearly empty supply of salt water, then do it all again. Technically some of the saltwater has been in my mixing barrel the whole 6 months I’ve been reefing. No known issues related to the water. I do have to clean heater and pump in the mixing barrel now and again of mineral precipitate.

 

[mike550]

Okay so two weeks ago I made water and did my water change. I had about 2-3 gallons left so I let it continue to sit and mix and today I need to make more water.

Would it be okay to add rodi on top of my premade water then add more salt or should I just dump the 2-3 gallons and make a brand new 6-7 gallons?

Because of the way my Brute is plumbed, I always have around 5G of saltwater left behind from a water change. I leave it covered, unheated, and uncirculated. I make "fresh" saltwater each week exactly as you described -- by adding RODI to the Brute, and then adjusting salinity and alk. So far so good!

 

[Gtinnel]

Me making water in my mixing station for my AWC is just like @mike550 where I never get all of the water out.
I'd guess that almost anyone who uses a mixing station has at least some residual saltwater leftover when they make a new batch.

 

[ehealy13]

Like most have said, I always have leftover and build off that. I use pumps, so it's necessary to have the pump submerged during the change(s). If you measure the input of water/salt there's no issue. If concerned, add slightly less salt, measure, and work to target.