Clown fish in reef tank using best reef salt

Best Reef Salt (Reviews & Buyer’s Guide)

If you’re looking for a hot topic in the world of saltwater fish tanks, ask reefers about the best reef salt. 

Saltwater aquarium owners often feel passionate about their salt mix choice. But then the question becomes – with everyone claiming their choice is the best reef salt in the history of the world, what is going to work best for you? Our favorite reef salt is Instant Ocean Sea Salt for Marine Aquariums, Nitrate & Phosphate-Free.

In this guide, we’re going to explore what to consider when evaluating reef salt mixes and look at the top picks out on the market today. 

Best Reef Salt Recommendations:

What is the best reef salt? 

The best reef salt for your tank depends on your tank set-up. Do you only have fish and no corals? Do you have hard corals only? Soft corals only? Once you have that narrowed down, you can start to select what will work best for your marine tank.

What is reef salt?

First, let’s start with the basics. 

Reef salt is arguably the most important ingredient for your saltwater aquarium. It makes your water salty and replicate natural reef waters. Without salt in your water, you wouldn’t have a saltwater aquarium and all of your fish and corals would die. 

Reef salt is composed of salts and trace elements that you will naturally find in seawater such as chloride, sodium, magnesium, and calcium. Sodium chloride is the most abundant salt. These are critical to sustaining life. 

The composition of these salts creates the salinity of your aquarium. Salinity describes the concentrations of dissolved salts. For context, ocean water’s salinity usually hovers around 35 PPT (parts per thousand).

Salinity levels are important to keep stable, especially during water changes. Like most water parameters (temperature, pH, etc.), drastic swings in salinity levels can shock and even kill your creatures. 

Also, the salinity level is constantly fluctuating in your tank. As the water in your aquarium evaporates, the salinity increases. Simply put, there is more salt and less water, so correspondingly, the remaining water is saltier.  This means that at some points in time, if your tank water has high salinity, you could theoretically directly replenish the tank with freshwater. The higher salinity waters in the tank will be diluted by the freshwater and bring the freshwater in line with the proper range. 

What does reef salt help with?

Different salt mixes are focused on different things, from corals to invertebrates to fish. Because of this, you will find varying concentrations of trace elements. For example, corals and invertebrates prefer higher carbonate and calcium concentrations, which is linked to healthy skeletons and shells. 

Some freshwater hobbyists even add salt to their tanks, claiming noticeable health improvements in certain fish, stress reduction, reducing osmotic pressure, inhibition of nitrite uptake, promoting the slime coat, and helping in healing wounds.

Synthetic Versus Mined Reef Salt Mixes

This is pretty straightforward. Was the salt mix produced from natural methods or was it produced in a lab? Mined reef salt mixes come from the mined, evaporated ocean water deposits. Synthetic salts are made in a lab and tend to represent some of the highest quality and most expensive reef salt mixes in the market. 

How to Pick The Best Reef Salt Mix for your Aquarium

Picking the best reef salt mix for your aquarium isn’t straightforward because it depends on the parameters of your tank and your marine inhabitants.

It is complicated though and there is a lot of marketing material to sort through, with all brands claiming to be the best, most pure, most easily mixed salt options. While it is true that some salt mixes are superior to others, there is no single best salt mix, because again, the answer really depends on your tank. The most important considerations include:

  • Calcium, alkalinity, and magnesium concentrations
  • Cost 
  • Marine Life in your Aquarium

Calcium, alkalinity, and magnesium

Calcium, alkalinity, and magnesium are the three most important components of your salt mix. Higher quality salt mixes have higher levels of each of these.

Saltwater also contains a large amount of dissolved bicarbonate – just like baking soda. This buffers the water against any major changes that could endanger your fish and corals. Salt mixes often refer to bicarbonate as alkalinity.

Below is a deeper breakdown of the importance of each element:

Calcium: Important for corals and invertebrates. Helps help build their skeletons. The recommended concentration is 400 ppm (parts per million).

Alkalinity: Alkalinity is a function of the amount of bicarbonate present. This is important because natural saltwater has a pH a little bit higher than 7 (somewhat basic). Alkalinity stops your water from dissolving your coral’s skeleton and poisoning fish. Without alkalinity, your water will be too acidic. The recommended range for alkalinity is 8-11 dKH.

Alkalinity is typically measured, rather than bicarbonate alone. Both calcium and magnesium add alkalinity to the water, so the amount of bicarbonate will vary depending on the ratios of the other elements. 

Magnesium: Magnesium is a trace mineral. This means it is found in small quantities relative to the heavy hitters like sodium, chloride, and calcium.

Magnesium is critical in order to keep your alkalinity balanced. It interacts with bicarbonate to prevent it from separating out of the tank as calcium carbonate, which would remove a lot of the salt and alkalinity that has been purposely added. Think of magnesium as a tank stabilizer. The recommended range is 1250-1400 ppm.

Cost per pound

You’re going to be using a lot of salt mix to maintain your aquarium so it is important to understand the cost. More than cost per box, you will want to understand cost per gallon. This will allow you to compare different size boxes of reef salt.

The standard box of reef salt can make anywhere from 150 to 200 gallons of saltwater, depending on the manufacturer. In order to standardize the cost, take the price of the box and divide it by the number of gallons it will create. For example, you’re evaluating a box that costs $40 and can make 200 gallons of saltwater. 200 divided by 40 dollars equals $0.20 per gallon.

That’s it. You now have a way to compare different sizes of reef mix.

Marine Life in your Aquarium

When you’re choosing a reef salt mix, consider the marine life in your aquarium. Do you own a fish-only tank? What about your corals? 

These are important questions because reef salt mixes contain slightly different amounts of calcium, magnesium, and alkalinity. 

If your tank contains hard corals, you’re going to want a salt mix with higher levels of vitamins and trace elements. You want to buffer your water more and provide elements that can help the corals bulk up. If you’re planning a coral tank, don’t forget about regularly feeding your coral too.

Depositphotos 115434030 xl 2015
Yellowtail Tang im tropical saltwater aquarium

It’s also important to think about total alkalinity. Hard corals thrive in higher alkalinity environments, whereas that higher alkalinity could be damaging to your soft corals and fish.

If your reef salt doesn’t have exactly what you need, you can purchase individual calcium and magnesium salts, as well as specific vitamin and trace element mixes. 

For example, hard corals’ growth depends a lot on the concentration of nutrients like calcium and bicarbonate. Lower concentrations equal less growth and less healthy corals. So you might need to introduce additional elements. 

Soft corals are more flexible and only produce a small coating of calcium carbonate skeleton. 

In a fish-only tank, the alkalinity balance is more important than the exact concentrations of calcium and magnesium. 

Best Reef Salt Options

Best Overall: Instant Ocean Sea Salt for Marine Aquariums, Nitrate & Phosphate-Free

Instant Ocean is probably the most famous of salt mixes because it is one of the very first artificial salt mixes created by the scientific community. This option from Instant Ocean is an excellent option for reef tanks with demanding hard corals.

It contains higher levels of calcium to help stony coral grow. Extra trace elements will provide nutrients and vitamins to support the health and growth of your corals, anemones, and other invertebrates. Users report success in mixed reef tanks with happy corals and fish.


  • Calcium: 425 ppm
  • Alkalinity: 14 dKH
  • Magnesium: 1440 ppm
  • Size: 200 gallons
  • Recommended Gravity Range: 1.020 – 1.024 at 77°F


  • Affordable
  • Dissolves quickly
  • Closely matches the ions of natural seawater


  • A few users have reported a brown residue

Best for Fish Only Tanks: Instant Ocean Reef Crystals Reef Salt 

This is another extremely popular choice because it provides the required elements at an affordable price. This is an ideal choice for fish-only tanks and soft corals tanks. Reef Crystals contains essential ocean reef elements in concentrations greater than those found in natural sea water. As a bonus, this option neutralizes trace heavy metals often found in tap water.


  • Calcium: 400 ppm
  • Alkalinity: 11 dKH
  • Magnesium: 1320 ppm
  • Size: 200 gallons
  • Recommended Gravity Range: 1.020-1.026 at 77°F


  • Low cost per gallon
  • Consistent results
  • Ideal for fish-only tanks


  • Some bad batches reported with damaging tank results

Best for Heavily Stocked Tanks: Red Sea Fish Pharm ARE11230 Coral Pro Marine Salt 

Red Sea Coral Pro is an excellent choice for heavily stocked tanks. It contains biologically balanced, elevated levels of the foundation elements (Calcium, Magnesium, Carbonates) necessary for sustainable, accelerated coral growth. It is a great choice for growing coral frags. 

If you’re keeping a heavily stocked aquarium, and you find yourself having to constantly replace nutrients, this is an excellent choice. 


  • Harvested from the waters of the Red Sea
  • No nitrates or phosphates (algae nutrients)
  • No toxic levels of Heavy Metals
  • No chemical binders


  • Ideal for heavily stocked reef aquariums
  • Provides lots of nutrients
  • Fast dissolving


  • More expensive
  • Extra nutrients not necessary if you have low stock or fish only tank
  • Many reporting the box arriving damaged (no damage to salt)

Kent Marine Sea Salt

This Sea Salt mix provides the necessary minerals that are present in the ocean. Kent Marine Sea Salt is easy to use and contains extra minerals for reef systems. This salt mix shouldn’t affect the alkalinity or pH of your water. However, a number of users have reported low calcium and magnesium once mixed so be sure to keep an eye on it if you go with this choice.


  • Calcium: 550 ppm
  • Alkalinity: 10 dKH
  • Magnesium: 1450 ppm
  • Size: 200 gallons


  • Fast dissolving
  • Provides necessary minerals that are found in the ocean
  • Nitrate and Phosphate free!


  • Some shipping damage reported
  • Some users report higher pH after using

Fritz Aquatics Reef Pro Mix Complete Marine Salt

Formulated by researchers and marine scientists, Fritz ProAquatics Reef Pro Mix contains all of the necessary major and minor elements of natural seawater. It has the correct pH and buffering capacity, essential minerals, and trace elements. It is manufactured in small batches for complete quality control. This salt mix is used by public aquariums, zoos, research institutions, adventure parks and hobbyists worldwide. 


  • Salinity 35 ppt 
  • Calcium 400-450 ppm 
  • Magnesium 1350-1450 ppm 
  • Alkalinity 8.0 – 9.0 dKH 
  • Strontium 9 ppm 
  • Potassium 400 ppm


  • Contains All Essential Major, Minor & Trace Elements
  • Reaches a Stable pH Shortly After Mixing
  • Enhanced Calcium, Magnesium and Potassium Levels
  • Nitrate, Phosphate & Ammonia Free


  • Some users report a poor shipping experience

Brightwell Aquatics NeoMarine – Marine Salt Blend for Reef Aquarium

Brightwell Aquatics NeoMarine Salt Mix creates an ideal marine environment by providing all major elements, all minor and trace elements, and elements known in natural seawater ratios. Elements are provided by individual salts with no seawater evaporite used. This salt mix contains no detectable ammonia, nitrate, or phosphate. 


  • Replicates natural seawater ratios of all major, minor and trace elements
  • Made in the USA


  • Maintains levels of trace elements to exact variables found in ocean water
  • Little need to add additional supplements such as calcium and magnesium
  • Similar performance to Red Sea products


  • Some users report a bad smell prior to mixing (goes away once mixed)
  • Salt is poured directly in the bucket versus packaged inside a plastic bag inside the bucket

Aquarium Vacuum FAQs 

Is aquarium salt the same as marine salt?

No, they’re slightly different products. Aquarium salt is sodium chloride with no additional additives. Aquarium salt is sometimes added to freshwater tanks for wound healing and disease control. Marine salt is sodium chloride plus trace elements that marine tanks need plus calcium and magnesium. Marine salt is essential to keeping a saltwater tank healthy. If you just add aquarium salt to a marine tank, your corals and livestock will not thrive.

Does reef salt go bad?

The answer is that reef salt can’t technically go bad, but exposure to various environmental issues like moisture can make it clump and be less efficient. Marine salt doesn’t contain additives, so the salt itself will not expire. However, if salt is exposed to moisture, it will clump, making it more difficult to mix effeciently. Over time, some reefers report that old, clumped reef salt mix is less effective at establishing the right water parameters.

How much salt do I put in my saltwater tank?

Most salt mixes call for about 1/2 cup of reef salt for every gallon of fresh water. Therefore, if you have a 55 gallon tank, you’re going to use 27.5 cups of salt when you’re setting it up. Use a measuring cup to measure out the salt precisely. This is a rough guide so you will want to double-check with the manufacturer and then test your water conditions directly in order to make sure you’re hitting the correct numbers before adding livestock and corals.

We also recommend using gloves to protect your hands. The grittiness of the salt can be abrasive to your skin.


Reef salt is essential to the health of your marine tank. It is as essential as a protein skimmer in your salt tank. Simply put, your marine corals and livestock will not survive without water parameters that resembles ocean water. Picking the right reef salt for your tank, depending on hard or soft corals, and aquarium stocking, is critical to keeping everything happy and healthy. 

Our all-around recommendation for the best reef salt is the Instant Ocean Sea Salt for Marine Aquariums, Nitrate & Phosphate-Free. This is great middle-of-the-road salt from a highly reputable brand. 

What reef salt do you use in your tank? Why is it your favorite reef salt?

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