Instant Ocean Sea Salt vs Reef Crystals (What’s The Difference?)

There are many things in the saltwater aquarium hobby that are considered to be a staple item and have been around for quite a long time.

Instant Ocean salt is one of those items. 

The brand Instant Ocean has been producing aquarium salt and other items for many years.

It is a trusted brand and thousands of hobbyists use their salt in saltwater tanks. Myself included. 

One of the great reasons why Instant Ocean salt is so great is that you can choose between using a salt for both fish only tanks and full reef tanks. 

They make Instant Ocean sea salt and Instant Ocean Reef Crystals. Both are suitable for all saltwater tanks.

But what is the difference between them? 

That’s what I will show you in this article.  You may or may not be surprised by how different they actually are. 

instant ocean sea salt vs reef crystals

What is the difference between Instant Ocean sea salt and Reef Crystals?

There are a few main differences between the two. But here is a direct quote from Instant Ocean themselves.

“Instant Ocean is engineered to closely match natural seawater, and reef crystals is enriched to facilitate the growth of corals and other invertebrates in a reef aquarium”

So think of it this way. Instant Ocean sea salt is perfect for fish only and FOWLR tanks just the way it is out of the box.

You can also use it for reef tanks provided you add the additional amount of elements needed to meet a reef tank’s requirements.

Reef Crystals is intended for use in a reef environment. Both salts contain these elements but the reef crystals contain more essential ocean reef elements at greater concentrations than natural seawater. 

Instant Ocean sea salt – fish only tanks

Instant Ocean Reef crystals – reef tanks

There are other differences which I explain below. Keep reading. 

How much does it cost?

There is a price difference between the two salts. Instant Ocean sea salt will be cheaper to purchase versus reef crystals.

Both are very affordable and are most times cheaper than other brands on the market. I always see great deals on Instant Ocean salt.

Instant Ocean salt is available in bags, boxes, and buckets. 

It is also available in different quantities from 10 gallons to 200 gallons which is great for all sizes of tanks. 

Check today’s price of Instant Ocean sea salt on Amazon here. 

Check today’s price of Instant Ocean reef crystals on Amazon here. 

Calculating the cost of these salts can be done easily. Just take the price of the salt and divide it by the amount of salt that it makes in gallons. 

For example, let’s say you buy a 200-gallon box of reef crystals for $70. That salt will cost you 0.35 cents per gallon to make.  

Perhaps you have a nano tank and buy a 10-gallon bag of reef crystals for $15. That salt will cost you $1.50 for each gallon you make. 

There is a cost-saving to buying salt in larger quantities. 

You can then use these numbers to figure out how much it’s going to cost you each month to purchase salt for your tank.

If you perform 2 water changes each month at 20 gallons each, you will need to make 40 gallons of saltwater each month. 

You could purchase a 50-gallon bag of Instant Ocean sea salt for around $25. Your cost per gallon each month would be 0.50 cents. You might have 10 gallons extra leftover from the bag which you can keep for next month. Every 4 months you would have enough salt leftover for an extra month. 

How do you mix Instant Ocean salt?

Mixing Instant Ocean salt is straightforward and easy to do. I recommend using a bucket or food-grade container like Brute to mix water and salt together. You will also need a heater and powerhead to mix the salt.

Directions from Instant Ocean website:

  • Mix Reef crystals with dechlorinated tap or purified water.
  • Use ½ cup of salt for each U.S gallon of water
  • Stir vigorously to ensure a good mix.
  • Although the Reef crystals can be used right away, we suggest aerating the water until it achieves oxygen/carbon equilibrium.
  • Measure specific gravity with an Instant Ocean hydrometer. (I recommend using a refractometer). 

What is the recommended specific gravity range?

Instant Ocean recommends 1.020-1.026 at 77 degrees F. 

I mix my saltwater to achieve 1.025 SG at a temp of 79F.

Note: 1.4 cups of Reef crystals will make 5 gallons of saltwater at a specific gravity of 1.021.

What is the proper way to mix Instant Ocean salt? How long do you mix it?

You should always add salt into the water and not the other way around. Adding water after salt can cause a highly concentrated solution leading to some precipitation of ingredients.

Instant Ocean recommends letting the saltwater mix sit overnight while mixing to allow for carbon dioxide equilibrium.

This normalizes PH and adds oxygen to the water.

What elements are in each?

There are certain elements in both the Instant Ocean sea salt and Reef crystals that are important for all saltwater tanks. The difference is that the Reef crystals contain a higher concentration. 

Read more on How to mix salt properly here.

instant ocean salt parameters

Instant Ocean salt calculator – How much do you use?

There have been questions regarding using a salt calculator to figure out how much salt you need to add. 

I recommend that you do not use a calculator for this. Always use the recommendations from the manufacturer to determine how much salt to use.

A general rule is to use ½ cup of salt per gallon of water. But it’s not set in stone for every type of salt. 

How do you test the salinity of Instant Ocean salt?

Testing the salinity of your Instant Ocean salt can be done using a refractometer. You can also use a hydrometer but they are less accurate and reliable. 

I recommend using this refractometer. It is affordable, easy to use,  and accurate.


There are a few differences between the Instant Ocean sea salt and Reef crystals. This includes the amount or quantity of elements in the salt. There are also price differences but the main one is the water parameter levels are different from both salts. 

If you have a fish-only saltwater tank and want to save some money, go with the sea salt mix. If you have a reef tank, go with the Reef crystals.

Both are great.