If you want to mix perfect seawater,  This article will provide you with great practical advice on how to ensure a consistent and perfect mix every time, while addressing some common issues and misconceptions (also available as a video):

Water changes – how much and how often?

To avoid unnecessary fluctuations in the water chemistry, we recommend a 10% water change once a week. If you prefer doing a larger change less frequently, we recommend you do not exceed 30% at a time.

Is R/O water a must?

In one word – Yes.
In ten words – never trust tap water, you never know what it contains.

What is the right temperature for mixing with R/O water?

The R/O water you use to mix Red Sea Salt or Coral Pro Salt should be no more than 20 degrees Celsius – or 68 degrees Fahrenheit. Once you get a clear mix, use a water heater to bring it up to your tank’s temperature and avoid unwanted heat fluctuations.

Mixing the salt – which goes first, the salt or the water?

Always add the salt to the water, never the other way around. And be careful not to overshoot the salinity!

How long to mix the mix?

Use a submerged pump, and mix only for as long as it takes for the salt to completely dissolve. Do not mix for more than 2 hours and do not bubble air into the water, as both of these actions will cause unnecessary precipitation.

Salinity – how to check it?

We recommend using a salinity tester that is specifically designed for seawater, such as Red Sea’s salt-water refractometer. Always confirm the calibration of a refractometer before using it. We also recommend you prepare a container with a volume mark, and a measuring cup for the salt, to ensure repeatable results with every mix.

Salinity – when to check it?

As a rule of thumb, check the new mix for salinity before adding it to your tank. If necessary, add a bit more salt or water to adjust the mix to the desired level. To stay on the safe side, also check the salinity level in your tank before adding the new batch, just to make sure everything’s in order.

Storing the mix

If you wish to make your RED SEA SALT mix ahead of time, store it in a sealed container to avoid natural evaporation, and place it somewhere dark, with a surrounding temperature of up to 25 degrees Celsius – or 77 degrees Fahrenheit. Under these conditions, the mixed water should be good for about 7 days. We do not recommend storing Coral Pro Salt for more than 12 hours, as it will precipitate and reduce the elevated levels of Calcium and Alkalinity, so it is highly recommended to make it just before use.

Storing the salt

In order to prevent clumping due to humidity, Always make sure that any unused salt is kept in a closed container, such as the Red Sea buckets.