Salinity increase.

[namfuak]

I believe what Randy is saying is that mixing 35 grams in 1 liter of water will be below 35ppt. I know that with my mix it's around 38.2g/L. If I used my salt mix and used 35g/L, I would end up somewhere close to 32ppt.

From what I have seen, the recommended ratio is a good starting point, but salt or RODI may need to be added to get to your needed concentration.

 

[ilott]

The problem is that some of the main ingredients in salt mixes contain a lot of water in the dry components. Magnesium chloride and magnesium sulfate are the biggies. They are about half water by weight.

Typical salt mixes, when made 35 grams per L, gives salintiy of about 28-30 ppt.

Craig Bingman measured it here years ago for many mixes:

Aquarium Frontiers Feature

Thanks I've just checked my salt bucket and I've read it wrong for like a year now ahahaha. Whoops. Oh dear. i'll start checking for 35 ppt before adding it to my tank from now on. Thank you for putting me in my place

 

[reefpizza]

I trashed mine hanna checker, just use a refractometer and a 35ppm calibration solution

 

[Randy Holmes-Farley Verified Community Expert]

I trashed mine hanna checker, just use a refractometer and a 35ppm calibration solution

Why did you trash it? There's no reason to think a random refractometer is better than a conductivity meter.

I've always been amazed that so many folks like refractometers. I recall saying in about 1992 that they were a tool of the past. Sort of like mercury thermometers.