How strong can I mix saltwater?

[Morpheosz]

I have a 50g barrel I use for mixing salt water and I use a Neptune DOS to change water every night. I also have a gravity fed ATO hooked up to my sump. Sometimes when my mix is a little off I just adjust the in vs out on my auto-water change routine to balance it out since my ATO will make up for any difference. This got me thinking, how strong could I mix the salt water in my barrel to stretch it out? For example, if I could double the amount of salt I could add half as much each night in my water change regimen. This would allow my water change barrel to, in this instance, last twice as long.

Therefore, my question is, does anyone have a sense for how strong I might be able to mix salt water before it's problematic (e.g. things not dissolving or precipitating out)? Would love to, for example, double the mix if that wasn't a problem.

 

[Doctorgori]

I don’t see any upside, Getting the salinity right would be tricky and besides I can see how you could add less than you remove…
But just out of curiosity I also wonder how saline you could mix commercial salts…

 

[Randy Holmes-Farley Verified Community Expert]

You cannot make seawater too much stronger than normal because the rise in alk and calcium will tend to drive precipitation of calcium carbonate. 2x may be ok depending on the CO2 level in the air and the salt mix used.

 

[Spare time]

I think precipitation will be an issue.

 

[Morpheosz]

I don’t see any upside, Getting the salinity right would be tricky and besides I can see how you could add less than you remove…
But just out of curiosity I also wonder how saline you could mix commercial salts…

The upside is simply i could mix up a batch of saltwater ever 3-4 months instead of every 1-2 months. The less maintenance I have to do, the more I enjoy the hobby :)

Getting the salinity right is trivial with DOS handling the water changes and the neptune monitoring salinity. Every time I mix a new batch of salt water, I usually end up tweaking the water change a bit if the salinity starts to drift in one direction or another. After a couple tweaks, my salinity is rock solid till my batch runs out.

 

[Morpheosz]

You cannot make seawater too much stronger than normal because the rise in alk and calcium will tend to drive precipitation of calcium carbonate. 2x may be ok depending on the CO2 level in the air and the salt mix used.

Thanks! Maybe I'll experiment with +50%. My CO2 is not too bad, I put an air exchanger on the house and it averages around 800ish. (vs 1200+ before it)

 

[Randy Holmes-Farley Verified Community Expert]

Thanks! Maybe I'll experiment with +50%. My CO2 is not too bad, I put an air exchanger on the house and it averages around 800ish. (vs 1200+ before it)

Well, high CO2 (low pH) makes it more stable.

I’m my system, even normal IO precipitated significantly at 35 ppt.

 

[Morpheosz]

Well, high CO2 (low pH) makes it more stable.

I’m my system, even normal IO precipitated significantly at 35 ppt.

Got it, makes sense!