Mixing salt at higher concentration

[Skydvr]

The past couple of weeks I have been mixing my salt at double concentration, then splitting it into two buckets to cut it to 35ppt. Using ESV B-Ionic. With my small space and small tank, I have found this to be a bit easier than trying to mix larger containers or multiple batches, though with B-Ionic it is quick. It also allows me to mix up extra water for cultures without adding any significant time or equipment to the process. Putting a large heater in the bucket gets the temperature up quick. I overshoot a bit as it gets brought back down when I mix in the rest of the RO.

I was wondering at what point does the mix become too concentrated and components start dropping out of solution or binding into insoluable compounds? I am setting up a larger tank, hopefully this weekend, and was wondering how concentrated I could go without seeing negative effects. I suppose I could set up a quick experiment and mix up a gallons worth in a quart of RO, let it stir for an hour or two, and mix it up to a gallon then test.


Is anybody else mixing a more concentrated solution then diluting back to where you need it?
Notice any differences?
What type of salt mix are you using?

 

[redfishbluefish]

I would not recommend this. The higher concentrations could cause for precipitation. I'm surprised you're not see ppt.

 

[Randy Holmes-Farley Verified Community Expert]

It is OK to mix slightly hypersaline seawater, especially in a mix that starts with NSW levels of alk (say, 7 dKH), but doubling does risk substantial precipitation of calcium carbonate, and the effect will be more of an issue in a high alk mix. If you do not see any precipitate, perhaps it is OK. If you see white precipitate on the sides or bottom, it is not.

After calcium carbonate and magnesium carbonate, the next thing to precipitate in concentrated seawater is gypsum (calcium sulfate), but that it takes more concentrated seawater than you are making.

 

[Skydvr]

The ESV has been mixing up clear with no precipitate. I haven't seen a difference in the numbers between normal mix and double concentration.

I was pretty suspect of going higher.
Although I just had the realization that with starting bare bottom until I can get some sand and more rock delivered from one of the aquaculture places down in Florida in tue next week or two, I can just mix in the tank to speed things up. The ESV mixes up quick and clean with no residue, so no issues like with the dry mix I was using before.

Randy, would temperature play into the precipitation at all?
Would a single part dry mix be more susceptible to precipitation due to higher localized concentrations when adding the mix?

I recently came across a liquid single part mix that is 8.7x. The mix is just added to RO and it is ready to go. How would they prevent precipitation in something like that but still have the magnesium and calcium available for the coral?