Obtaining a Saltwater "zero" for testing purposes

taricha · Feb 25, 2019

This is not about making clean saltwater for livestock or a tank.
This is to be able to create Saltwater for chemical tests and calibration. For these tasks it's useful to have a saltwater that you can be confident will have "zero" of some tested quantity, while having background chemistry in line with Tank or Seawater.
Here let's define "zero" as at least one (two is better) order of magnitude below lowest Level of Detection of hobby test kits.
Distilled + Salt mix doesn't pass that bar for lots of things. You can sometimes detect NO3, PO4 etc in fresh mixes.
Things I might want to be "zero": N (as NO3, NO2- NH4 etc.), P, Si, I, Fe.

RO/DI + table salt feels like not a very good approximation of saltwater, and getting a hold of all these seems daunting and unnecessary:

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Are there simpler solutions I'm missing? Does anybody make a saltmix that is intentionally blank of all the useful nutrients/metals - doubt it - people would kill a lot of livestock with that.

Larry L · Feb 25, 2019

What about Two Little Fishies "AccuraSea Seawater Reference and Calibration Solution"?

taricha · Feb 25, 2019

Larry L said:
What about Two Little Fishies "AccuraSea Seawater Reference and Calibration Solution"?

Thanks! that's a good lead. AccuraSea1 they say is...

Fast dissolving. At a salinity of S = 35, AccuraSea1 produces the following target parameters: calcium 420 mg/l, magnesium 1300 mg/l, strontium 8 mg/l, potassium 400 mg/l, Alkalinity 8 dKH.

Formulated by Julian Sprung with pharmaceutical grade sodium chloride and high purity anhydrous salts. Manufactured at Two Little Fishies in Miami Florida.

made from high purity anhydrous salts gives me hope.
however, they are marketing it as a Saltwater mix for reef tanks, so I'm guessing it has all the goodies I want none of. But I sent them an email to see if it might be a good zero for at least some of the things...