5 Simple Steps to Making Your Own Saltwater

Eddie Zia's 30 Gallon Reef Aquarium with EcoTech Marine Radion lights and VorTech pumps

Mixing up a batch of saltwater is not difficult. Some marine aquarists enjoy the process. Others... not so much. No matter how you feel about mixing saltwater, producing consistent batches of saltwater is important. Let’s explore several time-tested techniques that will make mixing saltwater easier and more consistent every time.

A Brute Trash Can is one of the most popular containers for mixing saltwater

1) Select The Proper Salt Mixing Container

Most marine aquarists use an empty five-gallon salt mix bucket to blend seawater. If you only need a few gallons at a time, a bucket or two will work out great. Any small plastic container that is sturdy enough to hold the water and large enough for your needs - Plastic carboy containers are also popular.

If you have multiple aquariums or a large reef tank, consider a larger plastic drum. You’ll be able to make enough saltwater in one batch, save time, and eliminate the hassle of mixing in multiple buckets. 20-50 gallon Brute brand plastic trash cans are super popular. You can get the plastic lid which helps slow evaporation and prevents debris from contaminating the water. There is also a caster wheel assembly which makes it easy to move around your house. 

Never use a bucket or mixing container with a questionable history, like something that stored used motor oil or hair dye. Ideally, the container should be new and never used for anything but mixing saltwater.

 

2) Use A Heater

Using ice-cold water to blend saltwater can slow the dissolving time a little bit, room - tank temperature water is best (70° - 78°F). This will speed up the rate at which the salt dissolves while helping to minimize precipitation. After the salt mix has been fully dissolved for 24-48 hours, you can then use it in your aquarium. Just be sure to check the water temperature with a separate thermometer to verify it's not too hot or too cold.  

If you plan to store the saltwater for any length of time after mixing, it is best to remove the heater and mixing pump. Use a tight-fitting lid and keep it out of extreme temperatures.

Cobalt Aquatics' MJ Multi-Purpose Pumps are one of the most popular choices for mixing saltwater

3) Use A Powerhead To Speed Up Mixing Time

Marine salts dissolve faster and more thoroughly when added to circulating water. Synthetic sea salt is a blend of chemicals with different dissolving rates and circulating the water keeps the particles suspended in the water, forcing them to dissolve more quickly and evenly. Use a submersible powerhead, like the Maxi-Jet, to circulate the water in your mixing container.

Always add salt mix slowly into the full volume of water you plan to mix preferably directly into the flow. If the marine salt is just dumped into the mixing container it settles on the bottom and resists dissolution.

Refractometers are an easy and accurate way to measure the salinity in water

4) Use A Hydrometer Or Refractometer To Measure Salinity

Salinity can be measured using Specific Gravity Units (SG) or salt concentration in parts per thousand (PPT). Always follow the manufacturer’s directions for the amount of salt to use per gallon of freshwater when mixing saltwater at home, the required amount of salt will vary between different brands.

Once the salt is fully dissolved, check the specific gravity or salinity with a hydrometer, refractometer, or digital salinity meter. It is important to know that the temperature of the water will affect your salinity reading. Most of the aquarium refractometers and hydrometers available will be calibrated at 75° - 78°F.  This means the water you are measuring should be up to temp. for the most accurate measurement. The farther away from that calibration temperature you get, the more inaccurate your salinity reading will be unless it is equipped with ATC - automatic temperature compensation.

Hydrometers measure the density of a liquid. Pure water has a density or specific gravity of 1.000 SG. As salt is added, the liquid becomes denser, and the specific gravity increases. The specific gravity of properly mixed saltwater should fall in the range of 1.023-1025 S.G. at typical aquarium temperatures. Hydrometers generally are not ATC or automatic temperature compensating meaning it's important your water temperature matches that of the hydrometer's calibration within +/- 3°F. 

A refractometer is an optical device that measures both specific gravity and salt concentration (salinity) in parts per thousand (ppt). Natural seawater has a salinity of 35 ppt. Refractometers are generally more reliable compared to most of the hydrometers made available to hobbyists. They can be calibrated and they include ATC or automatic temperature compensation which means they will account for small variances in your salinity reading because of temperature. 

There are two types of refractometers, digital and analog, and they both work via light refraction through a sample of saltwater. Refractometers are classically the most popular choice for aquarium hobbyists when it comes to salinity monitoring because they are quick and easy.

Finally, you have the digital salinity meters which are somewhat new to hobbyists, they have risen in popularity over the last 5+ years. These units find a salinity reading using conductivity and will often provide results in both specific gravity units or parts per thousand, whichever you prefer. Digital salinity meters are super easy, in fact, the easiest of the three options. That said, they do require frequent calibration checks, just like a refractometer. 

5) Keep all of your salt mixing gear in one place

Keep the dissolving pump, hoses, heater, and other gear all together in one place. Label the salt mixing container so it does not get borrowed to wash the car. You won’t find yourself searching through the house, basement, and garage looking for your equipment when it comes time to do a water change.

Building a Salt Mixing Station is an excellent solution as well. Here you can mount your mixing container, RO/DI system, and mixing pump as well as store salt mix and other supplies in a central location.