First Salt Mix - how much?

[kiwis]

Am I going insane. I've got a 140L (37us Gallons) system. Filled an running with RO water.

How much salt do I need to add? in cups ideally?

I know I want a salinity of between 1.021 - 1.026

I know how to mix it etc just can't see how much I actually add,

 

[Potatohead]

You will need a refractometer and some calibration solution to measure the salinity. It will be roughly 1/2 cup per gallon but that is not accurate enough to trust to house actual livestock without checking it.

 

[kiwis]

Yeah I've got a refractometer which I'll test it with. Just see how much I would need in there.

So if it's 1/2 per gallon and 1 US gallon is 3.78Litres.

So 140L is about 37 Gallons like I said, so half that for full cups and it's 18.5cups.

Seems a bit it and miss.

 

[Crashjack]

This is the calculator I use https://www.hamzasreef.com/Contents/Calculators/DirectSaltCalculator.php

 

[mike werner]

half a cup to a gallon will get you around 1.023 depending on the brand.you do not have to have an expensive refractometer.your local fish store should have the cheaper specific gravity checker if your on a budget.although not as accurate it still gets the job done.

 

[chipmunkofdoom2]

Seems a bit it and miss.

It can be, but it's not really if you put some thought into it. Before I got a large mixing vat, I used to weigh the salt mix by the gram. I use Instant Ocean and needed about 4.54 grams per ppt of salinity per gallon. So when I mixed 20 gallon batches, I used 20 gallons * 4.54 grams * 35 ppt = 3,178g. Using just a simple kitchen scale, this method was exceptionally accurate. Just measure out out the salt, and add it in. If you're not mixing up 50 gallons at a time, I would personally use this method.

Now I use a 44 gallon Brute trashcan to mix saltwater. One 50 gallon bag in about 42 gallons of fresh water makes water around 35ppt. So now I just fill the can with water, add the entire bag of salt, then I'm good to go.