Fresh Saltwater Mix, adding Alk, Ca, and Mg, in which order

[Bryn]

Disclaimer: I'm a physicist not a Chemist..

Got to thinking about precipitation, and had to ask for curiosity sake. @Randy Holmes-Farley

Making a batch of new Saltwater using IO salt (Instant Ocean), and have to correct the Alk, Ca, and Mg. Which do I add first, second, third, do I add all of the amount or half?

Thanks for pacifying my OCD..;Woot

 

[dragon99]

I'd do Mg, Ca, then Alk.
edit: unless you are lowering Alk, then do that first

 

[Randy Holmes-Farley Verified Community Expert]

You should not need to add alkalinity to it for any normal purpose. It will be unstable if you try to push the alk higher than it already is (which itself is unstable in raw salt water). If you did still want to do it, do it after the magnesium.

The order of the other two doesn't matter too much, but magnesium first is preferred to reduce precipitation of calcium carbonate.

 

[DivingTheWorld]

I usually mix up my IO just under the Salinity I’m looking for, then add Mag because Mag can increase the Salinity. Then once my Mag and Salinity are where I want them, I reduce Alk and increase Cal if needed.

 

[Bryn]

I reduce Alk and increase Cal if needed.

What do you mean reduce Alk, how do you do this. Thanks

 

[hllb]

Can I ask why you would do this rather than changing salt to something that more closely matched your targets?

 

[dragon99]

What do you mean reduce Alk, how do you do this. Thanks

I've used muriatic acid (hydrochloric acid) in the past to reduce the alkalinity in fresh Instant Ocean saltwater. It lowers the pH significantly though, so has to be mixed awhile afterwards. I've gotten out of the habit lately because the change in my tank's Alk after a water change just isn't enough to justify the extra time for me anymore.

I forget where I copied this from, but it was here on R2R:
The "acidity" (that being essentially negative alkalinity) of muriatic acid straight from the bottle is about 11,000 meq/L.

1/11,000 of the water volume of acid will drop alkalinity by 1 meq/l (2.8 dKH).

Do not drop more than 1 dKH per day due to the big pH drop in a reef tank, but in new salt water it is fine.

Aerate well after adding the acid to blow off the excess CO2 and bring up the pH.

 

[MJV15]

Can I ask why you would do this rather than changing salt to something that more closely matched your targets?

I agree with hllb, adjusting the levels in any mix to match what you have in your tank seems like unnecessary work. There are so many salt mixes with all sorts of levels surely there is one that closely matches your target parameters. Even if it’s going to a slightly more expensive salt by the time you factor in the money and time spent on additives. It’s gotta be close to a wash.

BRS breaks down per gallon cost of popular mixes- the cost per gallon difference isn’t that dramatic.

BRS has a whole slew of other videos looking at different aspects of popular mixes I found them all very interesting.

 

[Randy Holmes-Farley Verified Community Expert]

I agree with hllb, adjusting the levels in any mix to match what you have in your tank seems like unnecessary work. There are so many salt mixes with all sorts of levels surely there is one that closely matches your target parameters. Even if it’s going to a slightly more expensive salt by the time you factor in the money and time spent on additives. It’s gotta be close to a wash.

BRS breaks down per gallon cost of popular mixes- the cost per gallon difference isn’t that dramatic.

BRS has a whole slew of other videos looking at different aspects of popular mixes I found them all very interesting.

It may be unnecessary to reduce alk in a mix, but it may be cheaper, and may allow you to otherwise use a mix you like.

 

[Randy Holmes-Farley Verified Community Expert]

I forget where I copied this from, but it was here on R2R:

That is one of my posts.

 

[dragon99]

I agree with hllb, adjusting the levels in any mix to match what you have in your tank seems like unnecessary work. There are so many salt mixes with all sorts of levels surely there is one that closely matches your target parameters. Even if it’s going to a slightly more expensive salt by the time you factor in the money and time spent on additives. It’s gotta be close to a wash.

BRS breaks down per gallon cost of popular mixes- the cost per gallon difference isn’t that dramatic.

BRS has a whole slew of other videos looking at different aspects of popular mixes I found them all very interesting.

I love BRS videos, but that price breakdown just doesn't reflect what most people pay for Instant Ocean. At the current price on Amazon, IO comes out to $0.22/gal, less than half the cost of any other salt. Since most reefers already have 2-part additives laying around anyway, boosting IO to match what they want to see is quite simple and costs almost nothing. Personally I normally just add a little CA to it and move on. Mg can vary a little, but I'm not overly concerned with it.

That is one of my posts.

Thanks, I figured it was based on the wording. I've updated my note to include a citation