How To Mix Salt For Saltwater Aquariums (7 Steps For Best Results)

In this article, I will show you the 7 steps you need to take to mix salt properly for your saltwater tank.

how to mix salt for saltwater tanks

Mixing salt is something that you want to do correctly every time. 

In order to provide your tank with the best possible saltwater mix, you need to measure accurately and mix properly in order to keep your livestock healthy. 

Maintaining a constant salt level and avoiding fluctuations is important for a successful tank. 

Learning to mix salt properly will ensure you have constant water parameters without adding too much or not enough salt into your tank. 

Mixing saltwater at home is not only more efficient, but it will save you money in the long run versus buying it at a local store. 

You also have control over the type of salt being used and ensuring your water source is clean and free of phosphate, nitrate, or any other harmful contaminants. 

Providing you have all the necessary equipment, mixing your own saltwater is easy and once you have a routine in place, it becomes part of your regular maintenance schedule. 

Check out one of my favorite salt mixes on Amazon HERE.

7 steps for mixing salt properly 


#1. Use a proper mixing container

You will need to start with a properly sized container to mix the salt in. Depending on the size of your water change, the container should be 10-20% of your aquarium size. 

Small nano tanks can easily use a 5-gallon bucket or storage container. Larger tanks will require much larger containers. A popular water container to use is a Brute trash can or storage container. These often come with wheels that make it easy to move around. 

This one on Amazon is a good choice. 

Rubbermaid containers are another option. Just ensure that anything you use is safe for potable water or food and is not a low-grade container that can leach any chemicals into the water. 

The great thing about using a larger container is you can make extra water at the same time and have it ready for the next water change. 

Once you choose the right container, it’s important to only use it for mixing water. Never use it for some other project and then again for mixing water. You want to avoid the potential for any chemical getting into the water. 

Marine Depot Aquarium Supplies

#2. Fill container using RODI water only

Using RODI water will ensure that your water is safe for saltwater tanks. Tap water is never a good idea and it can contain harmful elements which can be a nightmare in a saltwater tank. 

RODI filters are affordable and easy to install. They will save you money in the long run and are very convenient to use.  Regardless if you have a fish only, FOWLR, or reef tank, you will want to use RODI water. 

Make enough water to complete your water change, plus extra for unforeseen spills and auto top off water. If you have enough room in the container, you can make extra for the next use. 

Aqua FX is a great RODI filter system at an affordable cost. Grab one on Amazon HERE.


“Reef aquariums are definitely the pinnacle of the hobby.” ~ Brian K. Vaughan

#3. Add your powerhead and heater

It’s a good idea to mix the salt with a powerhead. It needs to have enough water flow to mix the salt properly. Most people will just use an inexpensive powerhead that is not being used in your main tank or one that is spare.

Marineland Maxi jet powerheads are great for mixing salt.

Before adding salt to the container, turn on the powerhead to start aerating the water and add a heater to raise the temperature to match the tank. A rule of thumb is to use a heater that is sized at 3-5 watts for every gallon of water.

So if you are using a 20-gallon storage container to mix water, you will need a 75-100 watt heater to reach the desired temperature. 

I recommend using the Eheim submersible heater. 

Mixing cold water will take longer for the salt to mix and can shock your fish if added to the tank. An ideal temperature for mixing salt is between 65-70F. You can heat the water temperature to the desired temperature once mixed. 


how to mix salt for saltwater tanks

#4. Check instructions for salt being used

Before adding the salt into the container, check the instructions first to see how much salt should be added to get the right mix. You need to calculate how much salt is needed to reach a salinity level that matches your tank. 1.023-1.026 SG is a normal range. 

It’s common to add ½ cup of salt for every gallon of freshwater. For a 20 gallon container, you will need to add 10 cups of salt. Each manufacturer can be different so make sure to check before adding salt. 


#5. Measure and add salt

Using a measuring cup of your choice, add the proper amount of salt to the container slowly while it is mixing. As you add the salt, you will notice the water will go cloudy for a short period of time then clear up. This is normal. 

#6. Store unused salt properly

Once you open the bag or bucket of salt being used, it’s important to store any unused salt properly. Salt will naturally absorb moisture from the air if left unsealed and will turn the salt into a hard clump. To avoid this, make sure the bag is sealed properly to avoid air from getting inside. 


#7. Test water using a refractometer


refractometer for reef tanks


Once the salt has mixed thoroughly with the RODI water, you should test the salinity using a refractometer. It’s important to note that not all salts mix the same and some can take longer than others to fully mix.

On average it can take 3 or 4 hours to mix and others much longer. Some salts can take 24 hours before it can be used. Check the manufacturer’s recommendations ahead of time.

Once the salt is fully mixed at the desired temperature and salinity, it can be used. 

Using a refractometer, your specific gravity should measure 1.023-1.026 SG or 0.35 ppt which is the average salinity of seawater. 

HERE is a great refractometer. You can get one on Amazon.

That’s it. Once these steps are complete, your saltwater mix is good to use. Making your own saltwater mix is a safe way to ensure your water being used is the best quality for your fish and corals. It also prevents you from lugging water from the fish stores and will save you money overall.  


Best salt for saltwater tanks

There are a number of different salts mixes to use and some are better than others. Some salts are better to use with a fish only saltwater tank and some are better suited for a reef tank as it will have certain trace elements needed for corals.

Depending on your needs, choose the salt that has the proper amount of elements for your tank. Here is a chart showing the different levels of calcium, magnesium, and alkalinity for each brand. 



I recently wrote an article covering 7 of the best salt mixes which you can read here. 

My personal top choice of salt is the Red Sea and Instant Ocean. Both are available on Amazon and you can see today’s prices by clicking the link. 


Can you mix salt directly in your tank?

No, it is not recommended to mix salt in your display tank. This can cause spikes in salinity that are harmful to livestock. It is always best to mix salt in an appropriate container over a period of time. 


Following these 7 steps will help you mix salt properly with RODI water to ensure quality water for your saltwater tank. Once you have your water mixing station set up, keep your equipment in a safe place and available for use when you need it. 

  • Use a proper container
  • Fill using RODI water
  • Add a powerhead and heater
  • Check salt instructions
  • Measure and add salt
  • Store unused salt properly
  • Test using a refractometer