salt purification and collection

9 Best reef salt mix (2021 product review & comparison)

Ask the question: “What is the best reef salt mix for a marine aquarium?” on Facebook or any saltwater aquarium forum, and you are likely to get a whole host of answers.

The forums are littered with complaints and praises about nearly every brand of reef salt mix. In a lot of ways, this is because there are so many good options and the results we get in our tanks are so variable, we tend to assign our relative successes and failures to things we changed, when in fact it might not be the case. What you find is that each person on these threads speaks to how much success they’ve had when switching from one brand of aquarium salt to another.

I’m generally grateful to have the opportunity to read about their experiences, but it is often hard to discern anything scientific or even fair in their comparison to anchor to why the experience with one brand was so much better than the other.

How is a saltwater aquarium owner supposed to sort through the options to make the best reef salt mix choice for their own tank, based on your own goals, circumstances, and budget? That’s why I put together this comparison of popular reef salt mixes–to try and give you something specific to anchor on to help you compare across brands.

salt purification and collection

This is where salt comes from

Short on time? Jump to the conclusion and find the best reef salt mix for your tank

This is a fairly long article. If you want to cut to the chase and check out the marine salt mix I personally use in my home aquarium and recommend

Click here

To do your own comparison and check out a few different aquarium salt brands,

Click here instead

Comparing important water parameters across marine aquariums salt brands

Let’s start with an objective comparison across three important water parameters:

  1. calcium
  2. alkalinity
  3. magnesium
Tropic Marin Pro Reef Salt Mix in a bucket

This is an ultra-premium brand with a loyal following

Calcium (Ca)

Calcium is a critically important component in ocean water (and the aquarium salt that we use to make that water). Ca is used by corals and other invertebrates in the tank to build their stony skeletons.

Calcium from periodic table of elements

Did you know the molecular weight of calcium? It’s in this image

A typically recommended calcium level in a reef aquarium is 400 ppm. PPM stands for part per million, which in this case means 400 out of every million parts of the water will be calcium.

So it goes without saying (I guess I just said it though), that you should look carefully at the calcium levels in your desired salt mix.

Any brand with a level of around 400 ppm is good/ suitable. Significantly lower should be a red flag. Significantly higher is probably a good thing.

If you select a bargain salt with a low level of calcium, you’re going to have to spend additional time and money supplementing the water to get your desired levels. The other perspective of that point is that a salt mix with high levels of Ca is that you may not need to supplement your water to maintain appropriately high levels in your tank.

Alkalinity (Alk)

The alkalinity of the mixture is another important feature to consider. Alk is also, unfortunately, a challenging concept to describe in simple terms. It’s a chemistry thing, related to the pH, or relative acidity of the water. Here is how it works. The scale is about comparing to ‘regular freshwater.

testing for alkalinity

Alkalinity is also sometimes called ‘hardness’, measured in dKh

Almost by definition, pure water is not acidic or basic, but water with aquarium salts mixed in is considered to be relatively more basic or alkaline (it has more alkalinity). Alkalinity is important because it allows us to estimate how much bicarbonate is in the water–and bicarbonate is another one of those things that are important to coral growth.

The ideal range for alkalinity in a saltwater aquarium is 8-11 dkh. Which is a fairly broad range.

You would want to avoid a salt mix that makes your alkalinity too low or too high or is inconsistent between batches (which would cause the levels in your tank to swing back and forth.

reef salt mix comparison article

I took this picture of Instant Ocean salt mix myself…can you tell? Hahaha.

Magnesium (Mg)

Magnesium is one of the most abundant of the ‘trace’ minerals in saltwater. It ‘works’ with calcium and impacts the balance of alkalinity in the aquarium water. The recommended range for magnesium in a healthy saltwater aquarium is ~1250 to 1400 ppm. Since magnesium is generally readily available in a high-quality salt mix, you just want to double-check and make sure that it is also abundant in the brand you choose…just so you know it is not something you generally need to worry about, in the best reef salt mix brands.

That doesn’t mean it isn’t important, just that you likely have it covered.

How do the major aquarium salt brands stack up across these important parameters?

Several of the top aquarium salt brands are listed below, along with the values for calcium, alkalinity, and magnesium, as reported on their product labels. This list includes:

  1. Tropic Marin Salt Mix
  2. Instant Ocean Salt Mix
  3. Brightwell
  4. Red Sea Coral Pro
  5. Tropic Marin Pro Reef
  6. Reef Crystals Salt
  7. Kent Marine
  8. Seachem Reef Salt
  9. Coralife
best reef salt comparison chart number 1. Shows calcium, alkalinity and magnesium levels across brands

Look across these marine reef aquarium salt mixes to compare the levels of calcium, alkalinity, and magnesium compared with the recommended range

The reported values of calcium, alkalinity, and magnesium are listed in the reef salt comparison chart, for each brand and the recommended range/value is included at the bottom.  These are approximate values, not absolute. The first thing I noted was that all of the best marine salt mixes compared here post appropriate levels of each of the three water parameters: calcium, alkalinity, and magnesium

A few of the best reef salt mix options have standard ranges below the recommended levels. These are noted (in red).  I don’t expect the fact that a few drifted slightly below my previously noted ideal range to be meaningful. I doubt there are any data, anywhere, to suggest those levels are demonstrably less effective than the rest of the mixes.

So while you may be inclined to make a decision based on that (and you might as well, you don’t have a lot of other information to go on), I also encourage you not to over-react in the event the salt you are currently using (or intended to use) is on the low end of the list here for any of these values.

A few conclusions about these top brands

  1. I would feel comfortable purchasing and use any of the above reef salt brand options for a tank with mushrooms, zoanthids, soft corals, LPS corals, or SPS corals
  2. If I observed an issue in my tank that I suspected of being related to a value…like alkalinity…for example. I might test out a higher alk salt to see if it helps and go either up or down on the scale to see if that makes a difference.
  3. If I was dosing one or more of those nutrients into my reef tank, and I knew how quickly my tank depleted those nutrients, I would use it as one additional factor in calculating the cost (or cost savings) of one salt versus another.
Red sea coral pro salt mix

after using the salt, this bucket is great as a black round tub to raise fish larvae

Comparing the costs of the best reef salt mix options

Since all of the major salt brands listed above have the most important water parameters covered, one could make an argument that there is no single best aquarium salt mix and that they are all pretty much the same (I suspect the marketing brand managers would cringe if they read that). One thing you can objectively compare is the cost (I probably made the marketing managers cringe for a second time there).

At first glance, however, it can be slightly challenging to compare the cost across salt brands, because the standard ‘bucket’ of salt can make 150, 160, 170, or even 200 gallons of saltwater, depending on the manufacturer.

That makes the match nearly impossible for the average person (average dimwit writing this article, at your service). What I recommend you do to create a fair comparison is to take the price per bucket or box of salt and divide it by the number of gallons per container to determine the cost per gallon.

Here are a few hypothetical prices for each of the brands listed above that are approximated based on what I’ve seen. Please note, prices can fluctuate a bit online, so it’s typically best to go to the websites directly to do your own math and get the most accurate number. Below here is an example calculation based on some reasonable pricing estimates.

reef salt comparison chart number 2. Shows cost per pound and cost per gallon for popular salt mixes

Reef salt comparison chart

By creating the cost per gallon metric, it becomes a little easier to tell if the $77 bucket of Tropic Marin that makes 200 gallons is a relatively more or less expensive option than the $77 bucket of Red Sea Coral Pro salt that makes 175 gallons–or if the $40 boxes of Instant Ocean and Kent Marine Reef Salt are the same.

In the table above, I calculated the cost per pound of aquarium salt mix and the cost per gallon of mixed saltwater.

Factoring in the cost of adding supplements to your water

It wouldn’t be right to rule out a particular brand, just because they have a naturally lower concentration of a key element, because it is possible that you could add a supplement to the water mixed with that particular brand and achieve superior levels, at a better price–if the price is right.

Of course, the opposite is true as well.

For example, if you have a lot of stony corals (SPS or LPS) or clams, you may notice that the calcium levels in your tank steadily decline as the animals inside your tank deplete the natural calcium levels to build their stony skeletons and shells. In that instance, you probably want to supplement your aquarium water with a calcium reef supplement like kalkwasser (calcium hydroxide).

orange and white reef crystals salt mix box

Comparing prices can be tricky, this size will make 200 gallons of water (a little less actually)

Those who regularly dose calcium in your tank, you would benefit from doing one further quick cost analysis when picking the best aquarium salt mix for your reef tank.  So while my analysis above is just a straight cost per gallon, I encourage you to do your own math to figure out an ‘all-in’ cost per gallon once you account for supplements, if you add any.

If, for example, you buy Tropic Marin salt (at $0.39/gallon) and you routinely add calcium to your tank in the form of kalkwasser at an additional cost, it may be reasonable for you to consider switching to a brand like Seachem ($0.33/gallon), saving money and raising your calcium concentration by 165 parts per million–you may find you no longer need to add a calcium supplement between water changes, in that instance.

salt crystals on a black table

This is not a reef tank salt mix, but the image is pretty cool

So what is the best reef salt mix?

Take a look at the values in this chart and see for yourself:

Reef salt comparison chart


Tropic Marin ATM10581 Pro Reef-Bucket for Aquarium, 200-Gallon
Best Value


Instant Ocean Sea Salt for Marine Aquariums, Nitrate & Phosphate-Free, 200-Gallon


Instant Ocean Reef Crystals Reef Salt, Enriched Formulation for Aquariums, 200 gal


Red Sea Fish Pharm ARE11230 Coral Pro Marine Salt for Aquarium, 175-Gallon

For me, the best reef salt mix, of all the salts on the market, when you weigh all the various factors, is Instant Ocean.

Why is Instant Ocean salt mix the best?

Instant Ocean Salt is the best because it is a great quality product at a reasonable price. That’s the brand I use. I tried to ‘upgrade’ to the Reef Crystals brand of salt (also made by the same company).

I can report that I didn’t personally see any benefit to that more expensive brand compared with Instant Ocean Brand.

Instant ocean sea salt mix is the best overall value for the money

This is an extremely popular salt mix–and for good reason

Where to get more information about your specific reef aquarium salt mix

If you are interested in information beyond the scope of what is covered here in this review of the best reef salt mix, you may want to explore a few of the individual manufacturer sites for more information:

What reef salt mix do I use and where do I get it from?

For the last several years, ever since I pulled together that reef salt comparison chart, I have purchased Instant Ocean brand from (affiliate link).

No more lugging around buckets. The buckets come shipped directly to my door. No more drive time. No more hassle at all. And when the bucket arrives, I’m giddy, like a little kid on his birthday.

The product is Amazon Prime eligible (which means they will send it via 2-day shipping for free for Amazon Prime members) and also qualifies for their free Super Saver Shipping option too. What a great deal! You couldn’t beat that with an Acropora (get it? nickname..stick…).

which is the best reef salt mix

If you decide to buy a bucket of salt or any other product on Amazon after clicking on one of the affiliate links above, I will earn a small commission. No pressure at all. You can find the same products, at the same prices by searching on your own, but thank you if you decide to use one of the links to make a purchase. Every little bit of support helps me continue to produce this website.

Looking for more product review info like this?

If you found this article helpful in simplifying some of the noise out there about what you should buy, check out these other helpful articles:

What do you think?

How about you–what do you think is the best reef salt mix and why? Please leave a comment below to let us know what your experience is.

About the Author

Albert B Ulrich III

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Author of The New Saltwater Aquarium Guide, How to Frag Corals and 107 Tips for the Marine Reef Aquarium

the word salt written in salt by tracing the letters in the crystals on a black background

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