premixing water
 

I keep premixed saltwater all the time. I have a 33g reef and always have about 3-5 gallons mixed on hand. I use the 5 gallon white buckets from the fish stores that have a small 3 inch cap to seal it in with.

I add the salt, shake the container a few times every day or so and then only airate it for an hour or two (plus heat) before adding to the tank. The bucket gets some brown residue on the bottom after about 15-20 gallons without rinsing but with the cap on, nitrates have never been a problem for me.

You can buys these buckets at the fish stores for $5. (Got mine at big al's)

That's what I would recommend.

Re: premixing water
 

Measure the nitrates and tell me what ya got after its been sitting around for a week, so long as salt has been added

I'm curious to see what you get

Just tested mine that has been in a 5 gal sealed container, the square cube jug you get when you buy a pail Red Sea salt, that was made up little over 2 1/2 weeks nitrates 0

Well, I have RO/DI water, zero airation, zero heat.. sealed.. using Kent salt.. and there are nitrates after about 3 days.

Mine did read "some" nitrates enough to move it off zero but not enough to move to the next number, which I think is 20

I mix my water in a garbage can, I mix about 15gals at one time.
I used IO salt and tap water over 3 weeks ago. It has a powerhead and a heater running all the time. I keep it sealed and monitor the SG.

I just tested for pH and nitrate. pH was spot on at 8.2 and the nitrates read 0.
After reading this I will probably mix my water in smaller batches, but I am still happy with my system.

When I first mixed my Instant Ocean in my tank a few months ago, I followed the directions exactly : 1/2 a cup to 1US gal. My SG was so high the needle was almost off the scale on my hydrometer.
So I just do the add salt wait, test, add wait test, add wait test method.
Kind of a pain.

I have heard, that since salt is hydroscopic, it will absorb moisture from the air, and this will alter its weight and volume. So mixing by methods such as weighing and pouring x amount of cups is very inaccurate. Is this true?

You asked about the reading I have: I have two batches ready, one heated, one not. Both read 0 nitrates. They have been mixed for about 5-6 days.

I am curious if this is strickly a Kent issue.. Tho I have no plans on switching salt. Its no bother to mix the day of or night before.

20 would be pretty high.. What kind of test kit are you using?

When I used Oceanic salt I had that problem too, now I use Kents. I use Rubbermaid bruit garbage cans (food grade plastic) with lid and powerhead, and it lasts for weeks.